Nice piccy of the A330K, by the way M609.
Were you to ask your question of a senior bod in the MoD-box, you'd probably get a "Mumble, mumble.....big picture....chartering-in....Yes, please - and easy on the tonic....strategic assets...complementary fleets....another one will be very nice if you're paying" sort of answer!
BEagle's bolleaux feeling is that FS...let's stop calling it that, 'A330 MRTT' is primarily a tanker to replace the VC10 and TriStar tankers. The Primary Service Provider will be able to offer good terms on the movement of punters to various destinations in support of Tony's wars - but we've also got a fair number of A400Ms due. And do I hear whispers about perhaps a few more C-17s? Some C130Ks are undergoing life-extension, so there'll actually be a pretty capable AR and AT force in 2010-ish.
Don't know what'll happen to the C130J - but it also does some pretty useful work. (Damn - did I say that..??).