Four A2's for Maths at Oxbridge?

I took the same subjects as you and dropped chem for A2 and ended up getting an offer for 3 subjects. Stick with economics, even though you probably won't need it, purely because it's an interesting subject and the semi-essay basis is handy to keep in touch with. And if you are applying for maths, the further maths course won't be much hassle, physics shouldn't be too much of a headache, so only STEP and econ will be your workload. You should be able to cope just fine with that.

That's good to hear from someone who was in the same position as me and got an offer. May I ask where you applied, assuming you applied to do Maths?

I like the evaluative, critical thinking that Economics helps you develop, which is why I want to carry it on.