Similar story for me, got 2 a-levels at grade c physics and Biology. Do a levels that you enjoy, but make them academic subjects.... not media studies or art etc. A subject that shows logical thinking is always good, and nowadays the emphasis on management skills seems to be important in this industry so see if there is someway that you might be able to develop these.
I gained my PPL 2 years ago, and am slowly building my hours as the cash permits, i've spoken to a training captain at BA and he told me that the credentials that i have are what they are looking for (when they actually offer sponsorship!!) the PPL is a good bonus. If i can do it, anyone can.
If you have never flown before see if you can get a trial lesson at your local field, and tell the instructor what you want to do in the future..... i've gained some of the best advice off of these guys as they themselves ultimately want to get an airline job. Join the ATC, free flying!!
Go for it, keep your eyes open, look in flight international and on pprune then you should keep ahead of the game!! Get the qualifications and aim to go to uni you never know!!!!
Chris