Does it matter when the airframes were built? What we've got is what we've got; the best that is available within the budget constraints of the MOD. The RC-135V/W has been flying for a number of years and is the de facto "Gold Standard" for manned airborne SIGINT, what else should the RAF have aspired to in the current financial environment?
The platform is far more capable than the R1 ever was, don't believe all the hype about the RJ v R1. We're lucky to have been included in the RJ club and the UK will continue to gain from the joint UK/US investment until manned SIGINT is overtaken by events.
Daf