Correct me if I'm wrong, but there have only been contracts to put AAR kit six A310s, and all of these were already owned by the air forces in question: Canada (two) and Germany (four). This could just be because secondhand A310s are as rare as rocking-horse whatsit, but it doesn't look to me like the mod has inspired anyone else to follow suit.
As for the UK buying A310s for use in this role, you are joking, right? Ditch the PFI approach at this stage and 101 and 216 won't be seeing a new aircraft for a hell of a lot longer than the delay they're already facing!