How much does it cost to learn to fly in the UK, and what restrictions are there?
My recommendation is: Join a glider club. This limits the expense and puts you into contact with many like-minded people. Make sure the club has several gliding instructors, so you will have enough chance for training lessons.

Did you try the UK gliding club finder yet?

I prefer gliders over powered aircraft because they expose you to the weather and the laws of aerodynamics much more directly. Also, the expenses per hour are much lower. At most clubs, you can expect to pay around £20 per hour to hire a glider, around £30 for an aerotow launch and around £8 for a winch launch.