My opinion.
If you are interested in Engineering, go for Maths, Physics and two "soft" subjects that you can get A's in.
If you are interested in Social Science-y courses, go for Maths, Economics and two "soft" subjects.
My point is to try to gauge your grades. Do the two core subjects that you would need to get on the course and do easier subjects for other grades.
For example, some Universities tend to ask for an A in Maths and any other science subject. They don't care what the other subjects are, if you have selected two science courses. Maybe Oxbridge, UCL, Imperial and those unis may be strict with their requirements. Others may be quite lenient with their requirements.
Good luck