AN INSERT This application is a Divisional of Australian Patent Application No 2010210010, the entire contents of which are herein incorporates by reference. 5 FIELD OF THE INVENTION This invention relates to a booster seat for use in a vehicle, and or an insert or fitting for use with a booster seat. BACKGROUND A booster seat is a seat for children who have outgrown a dedicated children's safety car seat or capsule, 10 but still require support additional to that provided by a standard vehicle seat in order to improve the position of the child relative to a seatbelt intended for adults. Children in booster seats sustain serious but preventable injuries in car accidents where the lap belt of their seatbelt has been allowed to ride up on to their abdomen prior to the accident. From this position they can slip downwardly and out from beneath their seatbelt in an accident in a motion known as [5 "submarining". It would be advantageous to provide a booster seat insert for use with a vehicle seat belt, which contributes to a substantial reduction in the above mentioned risks, or which may, at the least, serve as a useful alternative. Other advantages of the present invention will become apparent from the following description, taking in 20 connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a child booster seat and insert positionable in use between a child and the booster seat, insert including: 25 a base portion having a seating surface for seating the child; and a vehicle seat belt guide adapted to retain a portion of a vehicle lap belt at a location between the legs of the child as the lap belt extends across the child's thighs, the portion of the vehicle lap belt retained by the vehicle seat belt guide positioned above the seating surface of the base portion and below the upper level of the child's thighs. In one form, this insert may also comprise a back portion which, optionally, is integral with or otherwise secured to the base portion. 5 In one form, the belt guide may comprise a loop through which the lap belt may be passed, where this loop is either a flexible or rigid member which may be adapted to be selectively open and closed. The booster seat and booster seat insert combination may be secured to a vehicle seat equipped with either of a lap-sash belt or a lap belt only. According to a second aspect of the invention there is provided an insert for seating a child relative to a L0 vehicle seat, the insert positionable in use between the child and the vehicle seat, the insert including: a base portion having a seating surface for seating the child; a back portion integrally secured to the base portion; and a vehicle seat belt guide adapted to retain a portion of a vehicle lap belt at a location between the legs of the child as the lap belt extends across the child's thighs, the portion of the vehicle lap L5 belt retained by the vehicle seat belt guide positioned above the seating surface of the base portion and below the upper level of the child's thighs. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is 20 capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain embodiments of the invention, and together with the description, serve to explain the 25 principles of the invention. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilised as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, to recognise that any claims should be regarded as including such equivalent constructions insofar as they do not depart from the spirit and 30 scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of this invention it will now be described with respect to one or more exemplary embodiments, which shall be described herein with the assistance of drawings wherein: 5 Figure 1 is a side view of a booster seat for securement to a seatbelt equipped vehicle seat; Figure 2 is a front view of the booster seat illustrated in Figure 1; Figure 3 is a partial cross-section (taken across A-A) through the base of the booster seat illustrated in Figures 1 and 2; Figure 4 is a partial perspective view of a base of a booster seat according to a further exemplary .0 embodiment; Figure 5 is a partial cross-section (taken across B-B) through a base of the booster seat illustrated in Figure 4; Figure 6 is a detailed top view of the reinforcing member from the booster seat illustrated in Figures 4 and 5; 5 Figures 7 and 8 illustrate what could be either of the above mentioned exemplary embodiments in use on a vehicle seat equipped with a lap sash seat belt; Figures 9 and 10 illustrate what could be either of the above mentioned exemplary embodiments in use on a vehicle seat equipped with a lap belt only; Figure 11 is a side view of a booster seat having an insert positioned thereon; 20 Figure 12 is a front view of the booster seat with the insert illustrated in Figure 11; Figure 13 is a partial cross-section (taken across C-C) through the base of the booster seat and insert illustrated in Figures 11 and 12; Figure 14 is a partial perspective view of a booster seat according to a further exemplary embodiment; Figure 15 is a front view of the booster seat in Figure 14; 3 Figure 16 is a partial cross-section (taken across D-D) through the booster seat illustrated in Figures 14 and 15; Figure 17 is a top view of the booster seat illustrated in Figures 14 through 16; Figure 18 is a front view of a booster seat according to a further exemplary embodiment; 5 Figure 19 is a front view of a booster seat according to yet a further exemplary embodiment; Figure 20 is a partial cross-section (taken across E-E) through the booster seat illustrated in Figure 19; Figure 21 is a detailed view of a belt guide in the form of a tab; Figures 22 a through d are examples of possible cross-sectional profiles for the tab of Figure 21, these being taken at point a-a; 0 Figures 23 and 24 are partial cross-section through a booster seat according to yet a further exemplary embodiment; and Figure 25 is a perspective view of a base of the booster seat illustrated in Figures 23 and 24. In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. -5 DETAILED DESCRIPTION Referring now to Figures 1 through 3, where an exemplary embodiment of a booster seat 1 for securement to a seatbelt equipped vehicle seat, is illustrated. The booster seat 1 may comprise integral base 2 and back 4 portions. The back portion 4 may have forwardly extending side wings 6, each of which is an integral continuation of the back portion 4. 20 A belt guide 8 is formed into an upper face 10 of the base portion 2 of the booster seat 1. The belt guide is a rigid tab extending from and above the upper face 10 of the base portion 2 so as to be defining a slot 12 between itself and the upper face 10 of the seat base portion 2, beneath which a portion of the lap belt of the seat belt may be passed, so that this lap belt portion is held close to the upper face 10 of the seat base 2. 4 The tab 8 is integrally formed with the seat base 2 so as to include a first portion 8a extending up from the upper face 10 of the seat base 2, and a second portion 8b extending from the first portion 8a in a direction substantially parallel to the upper face 10 of the seat base 2, so that the slot 12 between the second portion 8a and the upper face 10 has a forwardly facing open end. 5 The tab 8, seat base 2 and seat back 4 may all be integrally formed by a plastic moulding technique, and then covered with suitable padding, cushioning and covering materials to form the completed booster seat. Referring now to Figures 4 through 6, where an alternate exemplary embodiment 100 is illustrated, this embodiment being identical in nearly all respects to the exemplary embodiment 1 discussed above, except 0 for the fact that the tab 8 is reinforced by a steel reinforcing member 30. This steel reinforcing member 30 is a length of flat steel bar formed to as to have an upper shape which is complementary with and conforms to the shape of the underside of the tab 8. One end of the steel reinforcing member 30 is secured to the underside of the seat base 2 via a fastener 32 extending through both the seat base 2 and a hole 34 in the reinforcing member 30. In order to protect a child occupant from hard edges of the reinforcing 5 member 30, the tab 8 is formed with a downwardly curling lip 8c which curls over the end of the reinforcing member 30. This then would be further covered with suitable padding, cushioning and covering materials to form the completed booster seat 100. Referring now to Figures 7 and 8, wherein the booster seat 1 or 100 is shown secured in place on a lap sash seatbelt 40 equipped vehicle seat 50 by the seatbelt 40, which has a lap belt 42 and a sash belt 44. In .0 use, a child 60 (represented with dashed lines) sits on the seat base 54 facing forwards in the vehicle, and the child 60 is secured to the booster seat 1 or 100 and to the vehicle seat 50 in turn via the vehicle seat's seatbelt 40. The belt guide (tab) 8 retains a portion of the lap belt 42 at or near the upper face 10 of the seat base 4 at a position between the legs 62 of the child occupant 60. This causes the lap belt 42 to be wrapped closely 25 over the child's thighs and be kept low in relation to the child's abdomen. Referring now to Figures 9 and 10, where the vehicle seat 50 is equipped with a lap belt 42 only. In this instance, it is considered preferable that the booster seat be used in conjunction with a child harness 70 having shoulder straps 72 that extend down over the child's shoulders on either side of their head and terminate at loops 74, through which the lap belt 42 is passed. This harness 70 may be secured to a 30 vehicle belt mounting point via a tether strap 76. 5 Referring now to Figures 11 through 13 where there is illustrated a conventional booster seat 200, which has been equipped with an insert 300 which, in effect, converts this conventional booster seat 200 into a booster seat of the improved type 1 or 100 described above. This insert 300 has been positioned atop the base 202 of the conventional booster seat 200 and may be firmly secured thereto by known means (not 5 illustrated) including straps or portions of hook and loop fastener or studs or clips or a combination of these, so that the insert 300 cannot slide relative to the seat base 202. When secured to the seat base 202, the insert 300 is positioned, in use, between the booster seat occupant and the booster seat. The insert may include just a base or seating portion as shown in Figures 11-13, or alternatively the insert may include a back portion that is secured to the base portion. The back portion .0 may be integrally secured to the base portion. The insert may also be used without a booster seat if necessary, such that the insert is positioned is use between a vehicle seat occupant and a vehicle seat. A belt guide 302 is formed into an upper face 304 of the insert 300 so that these are rigidly connected. The belt guide 302 is a rigid tab defining a slot 306 (see Figure 13) between itself and the upper face 304 of the insert 300, beneath which a portion of the lap belt of the seat belt may be passed, so that this lap 5 belt portion is held close to the upper face 304 of the insert 300. The belt guide 302 as arranged in Figure 11 is positioned or extends above the upper face 304 of the insert 300. Alternatively, instead of a rigid tab, the belt guide may take the form of a loop through which the lap belt may be passed. The loop may be either a flexible or rigid member which may be adapted to be selectively open and closed. Any suitable mechanism for opening and closing the loop may be employed as would be .0 known to persons skilled in the art. A belt guide including a loop member would be located in a similar position to the rigid tab shown in Figures 11-13, so that the loop is adapted to retain a portion of a vehicle lap belt at a location between the legs of the booster seat occupant as the lap belt extends across the booster seat occupant's thighs. The portion of the vehicle lap belt retained by the vehicle seat belt guide is positioned above the seating surface of the base portion and below the upper level of the booster seat 25 occupant's thighs in order to prevent submarining of the occupant in the event of an accident. Referring now to Figures 14 through 17, where there is illustrated a booster seat 400 including a belt guide 8 that is formed into an upper face 10 of the base portion 2 of the booster seat 400 so as to be flush with (i.e. not protrude above) this upper face 10. The belt guide 8 is a rigid tab extending in the plane of upper face 10 of the base portion 2. The tab is defined by a recess 402 in the upper face 10 of the base 30 portion 2, where this recess 402 extends beneath and down two sides of tab 8, and then through a forward edge of the base portion 2 of the seat 400. In use, a portion of a lap belt of a seat belt may be passed beneath this tab 8, so as to be held close to but below the upper face 10 of the seat base 2. 6 Referring now to Figure 18, where there is illustrated a booster seat 500 including a belt guide 8 that is formed into an upper face 10 of the base portion 2 of the booster seat 500. The belt guide 8 is a rigid tab extending in the plane of upper face 10 of the base portion 2. The tab is defined by a recess 502 which extends beneath and down two sides of tab 8, through a forward edge of the base portion 2 and right down 5 through the base portion 2 of the seat 500. In use, a portion of a lap belt of a seat belt may be passed beneath this tab 8, so as to be held close to but below the upper face 10 of the seat base 2. Referring now to Figures 19 and 20, where there is illustrated a booster seat 600 including a belt guide 8 that is formed into of the base portion 2 of the booster seat 600. The belt guide 8 is a rigid tab 8 stepped down from the plane of upper face 10 of the base portion 2 so as to be extending at a level below this 0 upper face 10. The tab 8 is defined by a recess 602 in the upper face 10 of the base portion 2, which extends beneath and down two sides of this, and then through a forward edge of the base portion of the seat. In use, a portion of a lap belt of a seat belt may be passed beneath this tab 8, so as to be held close to but below the upper face 10 of the seat base 2. Figures 22 a through d illustrate various optional cross-section shapes which may be employed for tab 8. 5 This cross sectional shape may have an impact on the behaviour of belt portion(s) passing beneath this. Referring now to Figures 23 through 25, where there is illustrated a booster seat 700 including a belt guide 8 that is formed into an upper face 10 of the base portion 2 of the booster seat 700. The belt guide 8 is a rigid tab extending forwardly in the plane of upper face 10 of the base portion 2. The tab 8 is defined by a recess 702 which extends beneath and down two sides of tab 8, and in front of the tab 8. A spring .0 loaded catch 710 is located at the forward edge of tab 8, where this catch 710 is biased via a spring to form a closed loop with the tab 8. In use, the catch 710 can be pressed down and caused to rock rearwardly about a pivot point and against the bias of the spring so as to create an opening (see Figure 24) into which a portion of a lap belt of a seat belt may be inserted beneath the tab 8; when the catch 710 is released, this then captures the lap belt beneath the tab 8 and prevents the lap belt from escaping from 25 beneath the tab 8 unless the catch 710 is again pressed down. A significant advantage of a booster seat 1, 100, 400, 500, 600, 700 or indeed the booster seat 200 and insect 300 combination which is or are retaining or guiding a lap belt 42 in the fashion described herein, is that these prevents that lap belt 42 from riding up onto the child's abdomen, where this lap belt may cause severe internal injuries in the event of a vehicle collision. Moreover, causing the lap belt 42 to wrapped 30 over the child's legs in the fashion described herein significantly reduces the likelihood of the child submarining out from under the belt. 7 It will be understood that the term "comprise" and any of its derivatives (eg comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement 5 of any form of suggestion that such prior art forms part of the common general knowledge. Although an illustrative embodiment of the present invention has been described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims. 8