me_chambers
As has been said, doing your PPL in the UK is definately going to take longer than in the USA, simply because the weather will be better in the States, if not, it will at least be more predictable.
I have started mine here in the UK but am making such slow progress due to weather that I am currently researching finishing it in Florida, I hope to be able to finish within 2-3 weeks of flying.
It is common and good advice to fly a few hours in the UK before going to the States, as well as doing some or all of the PPL exams before you leave.
Also budget for some flying hours when you get back, to get in to the UK swing of things, most notably RT and circuit procedure.
Good Luck!
Simkin