Dont know what to pick for A Levels?Watch
As for doing Finance at university, I don't think they particularly prefer you to take certain subjects as long as you get the grades.
Have you considered doing anything other than Finance at university? If so, choose them for A-level so you still have the option if you change your mind. If you're really unsure, pick the GCSE subjects you got the highest grades in to carry on to A level as at least you know you'll do well.
Hope this helped!