Your employment history is far more important than your academic qualifications now and, in any case, yours are adequate. Don't waste your time and money with more A-levels; get on with the ATPL groundschool stuff.
And, while you're at it - and before you spend too much money elsewhere - get a Class 1 medical. It shouldn't be an issue for you, but you never know - it would be a shame to spend loadsamoney and put all that emotional investment into new hopes and dreams and find out that you have an eyesight problem that invalidates it all! Your SMO should be able to point you at an AME within the RAF who can do the required CAA Class 1, though you may have to go to the CAA at Gatwick for an initial issue. Check that out with the CAA or your SMO.
Scroggs