I can't really help on the specifics of your questions but if it helps I also inherited only one key with my used XF in January this year. I was quoted £235 for a spare which I didn't take up until the original key stopped working. I then purchased a new one from an independent Jag specialist which cost £160 for the remote key assembly plus £20 to programme plus VAT (£216 in total) Having read a recent Telegraph Motoring article on the price of car keys for other makes, the Jag key price wasn't too outrageous as a VW Polo was quoted as being over £700 and many other cheaper non-exec cars were pricier than the XF.