Yes but it's a bloody long way round. You'd have to join as a rating then after a while apply for a CW (commisioned warrant). This is no short term thing though. You are talking years, 3+ and even then you'd have to still pass all the other normal tests such as FAT's and AIB plus all the hoops you have to jump through as a CW candidate. The Army take on NCO aircrew but again you need to give, I think, 3 years normal service before transfering to pilot after passing FAT's and grading.
You could go the Brown route (either RM or Army Air Corps) and after passing all the nescessary (medicals tests, training serving as an other rank etc etc etc ) apply for pilot training.
It will take a lot longer and require just as much mental effort as studying for and then sitting A levels.
If you're at all capable of going the A level route first and then applying I'd recommend you do that.
I read somewhere on this forum (I can't find it now, nor can I remember who even posted it) that if you're a rating, apply for a commission and fail the chance of you being allowed to go back as a rating is slim. Is that true?
Secondly, out of curiosity really, can anyone from any branch apply to do FATs?