Although your question seems to have already been answered, I'd just like to reiterate that you should do whichever A Levels interest you most, as that's the way you'll do best (although one science subject, psych included in this, will keep your options open for certain unis). I'm doing Psychology, English Language and Classical Civilisation, and did RS at AS, and I have offers from Durham, Warwick, Birmingham, Manchester and Lancaster, proving Russell Group unis aren't prejudiced against certain subjects. All you need to do is prove your interest in the subject in your PS and get good grades in your A Levels and you should be accepted.