Strikes me that right now you want to get your feet off the ground more than anything else, build up some meaningful experience in the air, and then learn in earnest later on.
There are various ways to do this, such as...
- Air Cadets (not as much flying as they used to get, but still some)
- Air Explorer Scouts (variable, from lots of flying to really only normal Scouts with a different uniform - check out the local troop and see what they're up to)
- Most gliding clubs have cadet schemes allowing you to join and get cheap flying (a fun environment to spend your weekends too).
- Find out who your local flying club / microlight club / PFA strut are. See if they'll have you as a junior member, you'll almost certainly find lots of people happy to take you flying - especially if you volunteer to do a few jobs. You'd get lots of stick time that way, although most of it would probably not be loggable. (Although I know somebody who at about your age started trading floor-sweeping, plane-cleaning, phone-answering, etc. for lessons at a microlight school, by the time he was 19 he was an instructor.)
Like others, I agree that a lesson a month will not get you very far. Equally I don't think that an intensive US course is a good way to learn from scratch, although if by that time you are a fairly experienced glider pilot then all you'd effectively be doing is a rating - since you'd already know how to fly in British airspace - and it can then make sense.
But do look seriously at gliders and microlights, they are cheaper and still very much real flying.
G