Dr Peter,
I’m afraid you are going to have to do a lot of research as there will be many questions that only you can answer as it’s only you who knows your circumstances and what you want out of life.
However, if you haven’t already downloaded it, I recommend LASORS for UK JAA rules and regs regarding licences and all things aviating. It is a large .pdf file but worth it. Or you can buy it as a book.
First things first – have you flown a helicopter? If not, get a trial lesson – you might find it’s not for you.
Secondly – get a Class 1 medical (CAA website for details). If you can’t get this, your career ain’t gonna happen in the UK.
If you want to work in the States, better have a word with the American embassy with regard to visas.
If you want to fly a twin and are prepared to pay for it, then you can go anywhere you want! In the UK, it would cost about £800 - 1,000 per hour.
Cheers
Whirls