I have to agree with Scroggs on this one, go and study the exams that interest you. If not you will spend 2 years studying something that does not interest you and the fact that you are studying it for a specific purpose will probably make it seem harder and more of a chore.
A Levels do not directly demonstrate intelligence in a particular subject, they simply show that the candidate has the confidence and motivation to apply him/herself and the ability to retain information in order to answer the questions correctly, be it Physics or Music, Maths or French.. .2 Years is along time if you do not enjoy something.