Your best bet in my opinion, is to pay for the hours. Many of the US schools get away with employing people by not paying them, which is also how you get your hours.
If you have £40k to spare (from scratch, maybe less if you already hold PPL), you train in the US for a couple of years, get an FAA ATP with 600hrs multi, 500 of them in a turbine, like a B1900, and the JAA conversion, meaning that you end up with FAA ATP, JAA ATPL, 600 Multi, 500 turbine. Then you need to do an MCC course for a couple of grand.
Then you best bet during those two years in America, is either apply for the Green Card lottery if you are eligible, or fall in love and get married
There is virtually no chance of getting anything other than a cash-in-hand-slightly-dodgey instructors job unless you are eligible for residence.
One point, turbo prop aircraft in the states < 12501lbs do not require a type rating, though in JAR land, many do. So when you convert to JAR you may need to also pay for the type rating on the type you've already been flying for 500 hrs!
I wouldn't bother going to a JAR approved school in the US. What you get there is essentially the same training as a US school would give you, but you pay extra for those three little letters (J A R). Its just as easy and probably costs no more, to get all your FAA ratings and then convert to JAR later on. There's schools which now specialize in this....
Cheers
EA