Whatever you do, do not make the same mistake i made. I opted to study maths and physics at A level for the very reason that i thought airlines would prefer these subjects if i was to ever apply for sponsorship. Shortly after starting the courses i found that i didnt enjoy them, wasn't very good at them and could never possibly afford to self fund my training at such an early age.
At the time i had a complete change of career choice. I decided to apply to join the police service which i did and now, only a few years later, im just about to attend the first stages of assessment with NATS to become an air traffic controller (fingers crossed).
Best of luck whatever you decide but i can't stress how important it is for you to choose subjects you enjoy and subjects you are good at rather than picking them because that is what the airlines prefer. In my experience its about finding the right balance. Choose subjects that are going to give you the best possible chances and leave your career options open.