Honest advice:
For the moment, concentrate on your A-Levels - Pass them.
Go to university and do a degree - (start doing some flying ont he weekends etc - to gain the PPL)
After uni start to push for the ATPL.
This is because - you need something to fall back on, mind you some would say a degree now is not enough -
Then go for it - hopefully by then all the downturn in the econ. would have passed and you can then go for your dream.