Personally, I don't think anything higher than GCSE's are required. Some of the aspects of performance/navigation/weight&balance are a little bit complicated, especially at ATPL level, but you'll be able to learn what you need to know without too much hassle if you're interested enough. If you've got the GCSE basics (C or above) you shouldn't have too much trouble.
There may be recruiting requirements set out by some airlines/operators but I can't see a need for this, other than cutting down the numbers of people who apply, meaning less paperwork for HR to go through... Same is true of the RAF, they'll turn you down simply because of your eyesight. Now I know you can't be a complete retard, and get still a license/certificate but if you have the other basic skills and ability, regardless of school qualifications you should be OK.
As there aren't any good sponsorship opportunities around, you'll probably be looking at paying your way through flight school... If you can get your hands on the money, it'll all be possible. Quite easily.
My views are from someone (also from Leeds) aged 24, soon to be qualified as a Flight Instructor in America. No, not because it's easier - that's another story... I was turned down by the RAF (eyesight) and later I applied for CTC's wings scheme, which I also "failed" 3/4 of the way through, and still haven't received their amazing feedback, which I paid for and was promised... hey-ho.
For CTC I didn't have a degree/A-levels, and at the time they said they wanted 2 A levels minimum. I also had laser eye surgery, and passed the Class 1 down at Gatwick. Not a problem... So that's another possibility. Your eyesight must be within the CAA limits prior to surgery (so you're not gaining anything by having it done) but I'd recommend it. For one thing I owned up to it (many don't - but I already had a Class 2 with the VDL thing) and they told me they would never had known when they did the eye inspection. They couldn't see any scars, marks etc on my eyes. So that's another possibility.
I have 8 A-C GCSE's, studied A/AS levels but didn't put any effort into either, ending up with an E in AS physics, and General Studies. My advice is to pick easy subjects, as a pass is a pass regardless. I picked Maths, Physics, History and English Language. Big mistake. University is pretty much a joke as well for the majority of courses. So if you want to waste a few years getting a degree and drinking it's up to you. I joined the Army for 5 years, and got an HNC in Land Surveying out of it. So that was my university! The drive to fly was always there though regardless, if you're serious about it you'll know the feeling. And hindsight is a great thing, if I could go back to when I was 16, I'd certainly have put a lot more effort into school.
And as one last thing...
In my opinion, from a purely piloting perspective, it seems unfair that someone could be quite capable of having the flying skills of Chuck Yeager, supreme hand-eye co-ordination and be a really good "stick", but as they couldn't be bothered at school or didn't get the grades for whatever reason they'll never know.
It all depends on what you want to achieve as a pilot. If you want to become "just another number" with the airlines, study hard, try the various sponsorships, get a job to fund your flying and one day you'll get there.
Don't let anyone else tell you different.
If you wanna be a pilot and fly, and enjoy GA especially I can recommend the States. Much more GA friendly, NO flying club snobbishness, and it's not all about time-building and doing ATPL exams.
Whilst this seems like a rant from someone who is bitter and twisted, I just want to get across that nothing any career adviser says, or what grades you get at school should matter. So try as hard as you can at school (it will be worth it, even if you can't see that now) and don't blame it on sh1t teachers. Sorry bud, but that's a lame excuse. Maybe it really is down to you why you're not getting the grades??
Just be honest with yourself and work hard (as hard as you can for those C's or better) to achieve your goals.
You said you've got a Class 2 medical. Where do you fly out of? My advice, if you're not already, is go to Sherburn... Get involved more with GA and don't think it's all about ATPL-ing at this stage. Pride yourself as a pilot, and fly as well as you can. Consider tailwheel/aerobatic training. You don't often see guys who are genuinely good pilots... Many are just "adequate", so if you can be a pilot's-pilot and get a name for yourself because you fly well, you can join me and stick two fingers up to the world of degrees/A levels and the like!! I'd rather pride myself as a pilot (without being big headed, or unsafe) because I'm competent at what I do, than be bothered about silly pieces of paper with grades on. Plus, in later life you can look back and be proud of yourself. It'd be no fun if life was easy would it...?
Good luck with it all. Hopefully there's a line or two in all that which may be of help. Enjoy the ride...