This the subject of current research here at Manchester University. Basically, all the universities realise that physics at A level has become more qualitative, and that the maths A level itself has become a programme in search of a qualification, which is to say, not terribly useful beyond the final test. With that in mind, they are experimenting with various transitional practices designed to aid weaker students (maths support centres, diagnostics and targeted learning, peer support, etc, etc -- I've even heard of physics programmes spending the first year doing little other than maths). IMHO, if you are interested and will work, you already stand at a considerable advantage to many students on any given degree programme. Everyone is not expected to be brilliant at maths. Quite the opposite, in fact.