The VC10 and TriStar won't be replaced until at least 2011/12....assuming that the VC10s can actually stagger on for that long. The TriStars are in rather better state...just.
The contract for the FSTA A330 aircraft hasn't yet been signed. And it'll take at least 4-5 years for the first to be delivered.
Hopefully by then the RAF will be in a much better state than it is today.
Good luck, youngster!