PB, while flying training would no doubt provide a welcome distraction from your impending GCSEs, I would still recommend you get through your exams first.
Then, when you're ready to start PPL training see what cadetship/sponsorship course you can get yourself on to.
There are plenty of PPL scholarships on offer each year and you don't need to be the brain of Britain to be in with a chance of getting yourself selected.
In fact most of the scholarships are under-subscribed each year and as long as you're genuinely enthusiastic and you're willing to commit to intensive training over your summer holidays then you've got as much chance as anyone of getting a free PPL.
An Internet search will quickly show what's on offer in the UK. To get you started here are a couple of leads:
You can join the Air Cadets (there's over 1000 squadrons in the UK, see
www.raf.mod.uk/aircadets/ ).
If you contact the Caroline Trust (
www.carolinetrust.org.uk ) you could get some free gliding lessons.
The Guild of Air Pilots & Air Navigators (
www.gapan.org ) administer a number of PPL scholarships each year on behalf of generous individuals and aviation organisations.
Likewise the Air League (
www.airleague.co.uk ) administer PPL scholarships on behalf of generous donators.
Good luck, jez