I'd really advise against maths, I got a 9 at GCSE and also did Further maths and am still finding it difficult. If you haven't done any maths for a couple of years I think it would be really tough. People I know who did a mix of A-levels and BTECS always got higher grades in the BTECS because as long as you put the work in they are easier because they are a lot of coursework - so expect A-levels to be harder and definitely not something you can just fit around working full time.
I would go for softer subjects, particularly ones that don't have a GCSE version, so Business and Psychology might be good choices and I'd go for economics over maths - however if you want to do economics at degree level or apprenticeship then I'm guessing they'd really want a maths A-level - economics A-level is also very maths heavy I believe.
Personally I'd go into clearing this year and just see what you can get that you're interested in. You might be able to get a foundation year even if you can't get straight on a degree course. University's need to fill their places - I'd look at business degrees as well as finance/econ as fin/econ tend to be very competitive.
I'd avoid the apprenticeship route though, they're hugely competitive in finance/econ and you'll be up against people with 3 or 4 A*'s predicted plus all sorts of relevant and impressive extra curriculars.