I wouldn't worry too much about the GCSEs. IMHO it is just a lazy way of initial filtering to get rid of 'shell-suit-wearing-football-yobs'
One course of action you could take would be to get yourself on an aptitude test at one of the ATC schools (ASTAC or BAe Cwmbran). It'll cost you a couple of hundred quid but it'll give you a good idea of the intelligence level (rather than the qualifaction minimum) that'll be needed (and they may well have some contacts for companies recruiting). Bare in mind though, that passing the test is not anything like the pain you'll endure on a course! Oh no, the course is much, much harder!
If that works out, then contact every ANSP you can find an address for (google is your friend) and offer them your services. Not many, if any, will bite but if you go back to them - continuing to show interest and offer to partially (or totally) self-fund a course, they may offer you some kind of conditional deal. Of course, there is no guarentee that any of that will help.
That's a fair bit of work and only one way to go, but if you are serious and nothing else gets you where you wanna be....