After you've done your PPL you can expect to pay anywhere from about £55 to £95 an hour for your flying, depending where you go and what you fly.
As for whether to do it in US or UK, I think that depends how quickly you want to do it, and what you want to do afterwards.
If you just want to get a PPL as quickly as possible as a stepping stone for airline sponsorships, then go and do it in the USA as it'll be cheaper and quicker. If you want to do it so that you can fly in this country on your PPL, and take mates flying or whatever, then I would say that you are better off doing the PPL here in the first place.
Hope this helps a bit.
