Jaybird,
From what I can tell by reading various forums, only 3-5% of all applicants are chosen for cadet schemes and that is with A-level requirements in place. Why should the airlines make these odds even worse by expanding who can apply? Apparently they can find enough good people without lowering the application standard. Before trotting off to get A-levels so you can apply, I'd recommend doing the GAPAN assessment to see if you are in the top bracket of aptitude. If not, then just get on with self-sponsored training and quit fretting about A-levels.