Not a silly question at all!!!
As crewman said there are a variety of options available -
NATS
Non NATS airfield
Paying for your rating yourself (expensive and no guarantee of a job!)
RAF
Eurocontrol
It might be worth checking out what you want to do as it may affect your choice of A levels
For NATS it used to be 5 GCSE (including maths and english) and to have studied 2 A levels one of which must be either maths,geography, biology,physics or chemistry ( This may have changed - check to web site or contact HR)
Good Luck
louby