I'm an Irish guy who trained in California, I started my training last November and got my CFI and CFII about 2 months ago. My school - Mazzei Flying Service in Fresno, California, like alot of the 141 schools offer M1 visas for training but if I were to do it again I would go to a school that can provide you with a 2 year J visa which will entitle you to work for them as an instructor for the remainder of your stay once qualified. This will alow you to build close to 1000 hours during your time in the US which will then make it easier to find work in the UK or Europe upon converting to JAA.
Check out the Bristow Academy in Florida, that school used to be Helicopter Adventures and they also have another school up in Concord, California. Bristow also operate commercially pretty much worldwide and it would probably be pretty easy to make some good contacts for work in the UK while studying/working there.
Hope that helps.
Darren.