I did 5 at AS level and then looking to drop one later on. What did you get for GCSE? I did maths, further maths, biology, chemistry, physics and there were some links throughout. I think your subjects have an essay link so i think 4 would be possible. For me the work would get tough at certain points but I felt it was manageable. They will help your other subjects - just stay on top of it. EPQ is not worth it so if you are doing 3 I wouldn't even take EPQ... Geography seems to have a lot of next day homework at my school. Economics doesn't seem to be much work and maths doesn't have much heavy revision compared to English.