>I would suggest that they probably speak a more modern version of RP

Have you noticed that our Tone (Tony Blair for furriners) when making off the cuff remarks likes to use a bit of "modern PR" - sounds pretty estuary to me. I think that he likes to model his conversation style on the classic after-match interview, "Well, the lads had it all to do but in the event they pulled out all the stops, the other side were sick as parrots, we were pretty gobsmacked by the whole thing ....".