Thanks for all that Guys!
gcolyer: That clears up the visa issue in one sentence! Nice one. I was sort of aware of the need for a 'Airmans Certificate' or whatever the correct title is. When in the US doing my PPL, I recall one of the instructors complaining about the need to jump through massive hoops if he wanted to fly in Europe but "You guys can fly over here with a simple certificate for a few bucks" as he put it. I didn't take alot of notice at the time so didn't ask any questions.
CM: Followed the links, first class, much obliged, tells me all I need to know when the time comes and surprisingly straightforward. All I need to do now is decide when and where. Any suggestions as to where in the US is best? I'm open to ideas.