Thanks guys for your input.
It seems unless you win a green card on the lottery its a very closed market. I've looked at some of the majors recruitment web pages and to apply you need the right to live and work in the US, but to get a work visa which would lead to the green card you need a job offer, a catch 22 situation.
I've got to say I'm quite happy where I am, but you never know what the future holds and I've always had a liking for the States.
Seems the only other way is to marry an American. (I wonder how i could get hold of Julia Roberts number?)