A lot of airlines use the A-levels as a way to narrow down and reduce the sheer number of applications. It's not unusual for these schemes to have a couple of thousand applications for say 10 positions...so when you look at it, less than 1% make it through selection.
There is a lot of study to do in a very short period of time, and these schemes are usually limited to applicants under 26 (though not sure if this is still legal under age discrimination laws). Therefore, they use A-levels to see who has a proven track record of being able to study successfully. You have to realise that they are often spending £50k just to get you through to CPL/IR standard, then there is a type rating on top of that. No one simply writes off around £80k to anyone who has a dream to fly.
On the other hand, I was in your shoes and spent 10 years working in IT saving the funds to pay for my own training. I now sit in the right hand seat on a B757. I have a huge loan to repay, but it just shows if you want it that much, it may take some time. Sorry if this isn't what you want to hear, but best of luck.