Agree with Heliplane about what he has said about school and flying, as much as you love it, your A levels will interfere, but by doing them well first time it will make life much easier. I didn't do any flying during term time of my last year at school, and I believe it has made a difference. Its better to pay for a check ride after being away from it for several months than to pay in then long term for poor results.
Also as you get nearer the 17 age mark start finding out about scholarships and how they may be able to help you get your license. In particular I can recommend the Air League, who have made alot of difference to myself, and many others I know. (Also worth looking at for other qualified pilots - they provide bursaries for IMC ratings/Night Ratings and Aerobatics for pilots well into their forries. PM me for more information)