Seeing your other options I'd think that history links more into your chosen A Levels than maths, but it's whatever you want to do, after all. If you feel like four essay subjects would be too much, or that maths would be too far out of left field to keep up with, then base your decisions on those. Maybe talk to your teachers as well?
And yes, maths is harder than GCSE, and you won't have the advantage of doing AS exams like I did, but that's the same for all subjects now, so something to bear in mind. We haven't done the same specification for maths as you will be doing.