Well what i would advise is pick some A Levels that you want to do and are good at. If an airline were to go and look at your A Levels i am sure they would rather see some top grades in something you are interested in than seeing some below average grades in subjects that you did not enjoy. It is not essential to have maths or physics to be an airline pilot, however they may come in use when you come to do your ATPL theory as some subjects covered use similar types of methods.
Regards