Hi Bicky. I just bought a Jaguar XF two weeks ago and had the same problem, didn't want to rely on the can of foam. Jaguar quoted me £450 plus vat for a space saver and wheel kit which is ridiculous. Bear with me this is what I did. The wheels I have are 245/45/18. Measured across one of my wheels to see if it would fit in the wheel well in the boot (only just). Bought an alloy rim same as I got on my car from ebay cost £150. Bought a tyre locally, cheap one as its a spare, cost fitted was £55. Next you need a wheel retaining bolt which you can pick up online for £12. This wont be the right size as it's designed for a space saver, but you can either get it cut down or put a block of wood with a 8mm hole drilled through it and brace the wheel down. Lastly got a jack and wheel brace from ebay at a cost of £15. Total cost £232 for a full size spare wheel. When you take the liner out of your boot well make sure the wheel will fit (i'v read on hear that some models got an amp eating into the space, mine hasn't). I put the wheel face down and tightened the bolt through the wood to secure the wheel, you can either buy a boot organizer to store the jack and brace but what I did was buy a piece of high density foam cut to size for the inside of the wheel (ebay) and cut out the shapes for the jack nd brace. Sorry this is a bit long but I put in as much detail as possible, if you need any of the websites I used please let me know. Any comments welcome.