Hi,
I wanted to do a similar thing to you when I was your age but I was held back by crap eyesight.
I know that the Army Air Corps will accept pilots who have less than perfect vision so that could be an option for you (depending on how much your eyesight deteriorates) as at the moment I don't think laser eye surgery is acceptable for pilots in any of the UK armed services.
However, as you're only 13, things could well change by the time you're old enough to join up as some air forces (US I believe?) will accept pilot applicants who've had laser eye surgery.
Good luck