One thing to add to your consideration is the very real prospect that once in Florida, it might be viable to buy a decent time builder plane, and tour around while building time. This kind of independant experience building will make you a much better pilot, and thus instructor. I'm always leary of the 300 hour wonder instructors, who, themselves, have hardly left the circuit. If you own a plane, you can go on extended cross countries (and there is a LOT of country there!) and you'll be amazed what you'll learn!
Time building on a plane you own is much cheaper than renting. When you're done, sell the plane for what you paid for it! As it sounds like flying is more expensive in the UK, save your money, and put it toward buying in the US. You can always hire an instructor, to train you as you need on your plane.