Here is some information about jobs. There are 25,000 helicopter pilots in the USA today. 20,000 are commercial pilots. 5,000 to 10,000 of them are Vietnam era pilots and will be retiring in 1-5 years. The future is very rosy for helicopter pilots. There is a few things to consider. You will need around 1,000+ hours and an instrument rating for lots of them. The companies in the Gulf of Mexico are desperately short of pilots. There are not enough EMS pilots but you will need 2,000+ hours and you won't fly much. There is a shortage of instructors as most of them can't wait to move on and be ex-instructors.
A lot has been said about permanent residency in the USA. The marriage route is sadly about the only available one for Brits. Anything else is very difficult if not impossible.
Good luck,
Chopperpilot47