There is no real answer to your situation. If you are determined, and it sounds like you are, I’m sure you will find a way of becoming a pilot. I wouldn’t be too concerned about A levels, I did my ATPL subjects at age 19 with one A level in photography and passed them all with high marks. If you study them through a good provider they will teach you everything you need to know. I am yet to hear of an airline who gave a crap about what A levels I had and very few care what my ATPL results were. The situation is somewhat different if you intend to apply to the RAF or airline sponsorship (should this start again).
If you’re going to be self sponsored, which almost everyone is now, your biggest hurdle is going to be money as you going to need lots and lots of it. You will find nowadays, with no airline sponsored students, commercial flying is the realm of the rich kid or the disillusioned 30 something. Money talks and these people are able to comfortably buy a fATPL, MCC and Type Rating without bating an eyelid. This is what you’ll be competing with and talent and ability is not a precursor for success in this industry, unfortunately.
At 16 you’re very young. You have a good 10-15 years before you need to start worrying. In that time make a crap load of dosh, as many contacts as you can or marry a chief pilot’s daughter!