as someone who got a B in GCSE maths, was thoroughly bored of it and hated it, and then went on to study engineering, all of the above "if you don't get an A* you can't do A-level maths" is ridiculous.
To begin with, that level of maths is much more interesting and engaging than the GCSE topics in general (although it's improved somewhat in the new syllabus I hear). So that could well make a world of difference in itself. While it certainly requires a concerted effort on your part, that is true of any subject. So, again, not a reason to not pursue it.
As above, you need A-level Maths to do Geophysics. You need it to do Geology; you just don't need it as early as you do for Geophysics (where you need it before starting, rather than later in the course. You can't not do those areas of maths and pursue those subject areas. The closest you could get would be to do some artsy "Physical Geography" degree or something.
Now consider, at university, you have to do a good chunk of the core A-level Material, in 50-25% of the time, and with much less individual attention. You also miss out on some of the wider contextual work you'd do in A-level Maths. There is literally no reason not to do the A-level route - contrary to prior assertions, the A-level Maths route is actually the easiest to follow, in terms of subject knowledge and understanding. Are the exams harder? Difficult to say - it would depend on the university/course/module leader/exam board/etc, etc. However you have much more support in 6th form than in university in general, and you get given a lot more of the content directly, rather than only being presented with the bare-bones, core material and being expected to do a considerable amount more work yourself.
You can always ask your school if you can start with 4 subjects and drop one (either taking the AS exams, or not). However of those subjects, History isn't relevant to your proposed area of study. It would only really "fit" if you wanted to pursue e.g. Archaeology, and bear in mind it's not a requirement for that anyway. It's only required for studying History itself (and various joint honours and similar courses in History). While the strongly academic essay based subject is good in general for preparing for higher study, in STEM it's much more important to have core curricular knowledge beforehand, rather than transferable skills (the latter of which is all you're getting from the History course).