Personally I would go the US/FAA route. The US dollar is really weak right now, you'll probably find that it wont cost as much as you think. Also housing and food is cheaper in the US.
If you train in California, Florida or Arizona you'll be guaranteed to get the most flying weather from your stay in the US. Something thats often forgotten by prospective students.
Personally I would:-
1) Complete FAA PPL, Anglo American in Cali or Naples Air Center in FL. Both are authorized to issue M1 student visas..
2) Complete FAA Instrument Rating, this will help lots in understanding the ATPL groundschool.
3) Complete JAA ATPL ground school, as far as I know the only school doing this outside the UK is Naples Air Center in FL. Bristol distance learning is reputable..
4) Complete JAA Commercial License, theres a number of JAA examiners working in the USA right now.
5) Convert FAA Instrument rating to the JAA in the UK.
This will gain you a JAA frozen ATPL. As for working in the USA, forget it without a J1 visa or green card!