Hi! As a year 13 student who does maths, I can tell you that there is statistics in the maths A-Level course. They used to do pure maths (algebra) and applied maths (stats and mechanics) as separate a levels but now there is just ‘Maths’ which combines both pure and applied maths.
Especially if you’re doing further maths (which also includes more statistics in it), personally I don’t think you’ll need an extra a level to do something like finance or accounting. I’m applying for economics and I have friends doing finance and accounting and we all do maths or further maths and that perfectly fine for Russel Group unis and even oxbridge.
If you will take Maths, Further maths and geography, that’s perfectly fine but if you wanted a 4th, consider economics if your school offers it. Otherwise 3 A levels is completely fine. Doing one outside of school is an extra pressure which I promise you won’t want in year 13.
So if you want to do 4, i would recommend doing them all in your school (Maths, FM, Geog and Econ) and don’t worry about the ‘statistics’ part too much because there is stats in the maths and FM courses and unis don’t expect a standalone stats qualification.
Sorry if this is confusing but hope it helps!!