Tartanterror
I've done a bit of research on this topic myself, so I can give you some answers but, as 'AirPig' mentioned, Chris Pocock is the real authority on this topic.
Robbie Robinson and John McArthur are, as far as I am aware, the only RAF pilots who took part in actual overflights of Russia - the others probably took part in some interesting sorties along the border of the Warsaw Pact, but these were probably after Frank Powers had been shot down.
Robbie Robinson died a while ago. John McArthur was alive about 7 years ago as I understand he was asked to give a presentation to the RAF Historical Society at their seminar on Cold War Intelligence Gathering held at the RAF Museum on 18 Apr 00. Sadly he had to decline as he could not obtain the appropriate approval from some 'minder' at MOD, despite the fact that these activites took place place some 40 years ago and are reported in detail in various books and publications!!
I do hope both Robbie Robinson John McArthur have written detailed accounts of their time on the U-2 that eventually find their way into the public domain. However, the 'official' line seems to be that these overflights by RAF pilots never actually happened! The offical MOD file on RAF U-2 operations has still not been released into the public domain, despite Chris Pocock's best efforts.
I have known Chris Pocock for a while and met up with him earlier this year for a natter, so if you PM me with your e-mail address, I'll give him a bell and see what he has to say. He attends most of the U-2 reunions in the USA, so he probably has the answers, but I suspect most of these guys have already passed away, without leaving a written record of their time on the aircraft.
In the meantime, you might like to have a look at my article on the U-2:
www.spyflight.co.uk/u2.htm
Heimdall