Leaving A level mathematics a week before the exam.

I have been doing biology, chemistry, economics and maths at international A level and I find that the majority of my time goes towards maths. I have my P3 maths exam in less than a week but I'm thinking of not continuing maths at a level as I've already achieved the AS and I don't need it for the university courses I want to do. Is it too late to leave it now? Will I have to pay a penalty or anything like that if I drop out and don't attend the exam?

Yes Ive already applied. Maybe I should just do the P3 exam and then drop it, so I'd have 4/6 of the qualifications I guess. I'm unsure if I'd have to tell the unis by email or if I'll have to pay a penalty to get back into UCAS and change it?