Hi! I'm going to study Psych at university in September and I do Psychology, History and Classical Civilisation. I did maths at AS but dropped it after the exam. The only a-level I do now that relates to studying psych at uni is psychology itself. Maths from AS did help slightly with the A2 side of the psychology course and I'm guessing will help at uni as it may make it easier to understand some statistics and calculations. But in general, the universities I applied to did not seem to mind that I had only done psychology that relates to their degree. They are more focused on the grades and also your personal statement. However, if you are looking to go to a university that is a russell group, then they may want biology, but if not, it shouldn't really matter. They are your A-Levels so you should pick whichever ones you're interested in the most as at the end of the day, you have to sit the exam. (Sorry for the long reply).