Hi There,
I am also 16 and studying for A-Levels but I am doing maths and physics. From what I have read here I don't believe the maths gets any harder than GCSE level and maybe a bit of trig for working out crosswind and headwind components. I don't think it will put you at a huge disadvantage maybe just a bit slower at realising than the guys who did the maths A level? I would try to practise some mental arithmetic every day just to keep your maths sharp as I doubt you are using it now. When I go down to the petrol station near my college for lunch I always add the bill in my head and also do the same of my friends. It just helps to keep your basic maths sharp.
There is a very useful thread here about degrees
http://www.pprune.org/professional-p...rsity-not.html
I would take a few hours to read it all
I don't believe school matters that much, ryanair takes guys from anyway. Although the only time I can think of a well known provider being an advantage was for BA SSP a while ago. Hopefully someone else can clear that up a bit better than I have
You are only 16 so not flying experience isn't a problem now, I have about 4 hours in a PA-28
Good luck!