Hi Tom
Im also in my last year of college, im 18 and also hold a PPL (a lot of us around these days!)
Its by no means perequisite to do Maths A Level, i do Physics as A level though as i like it, however do the subjects u enjoy! If all goes to plan i should be going to Oxford this summer on the APP, might see you there!
PM me if you have anymore questions
Good luck