please help (further maths A level enquiry)

I have just started year 12, and I am currently doing Maths, Economics, and Business studies for my A levels. I've realised that many top universities do not accept the combination of Business and Economics such as LSE and UCL. My GCSE grades were also pretty bad (7776666664 - 7 in both Maths and English Lang) which means that if a Uni doesn't like the combination of Economics and Business, my GCSEs arent going to give me much of a chance to get a place. For this reason, I am considering taking another A level, but no other subjects seem anywhat interesting to me, apart from A level Further Maths. My problem is in my sixth form you need an 8 in GCSE maths to do A level further maths, a requirement which I do not meet. I was thinking that I self cover some year 12 content during the space of the year, and then in the y12 summer holidays I can fully understand the year 12 further maths part of the A level and then try and do further maths with my sixth form for y13. Is this possible, or am I being delusional. For instance, I have done extremely well on my first set of assessments/mocks, receiving A* in all 3 subjects.

I have just started year 12, and I am currently doing Maths, Economics, and Business studies for my A levels. I've realised that many top universities do not accept the combination of Business and Economics such as LSE and UCL. My GCSE grades were also pretty bad (7776666664 - 7 in both Maths and English Lang) which means that if a Uni doesn't like the combination of Economics and Business, my GCSEs arent going to give me much of a chance to get a place. For this reason, I am considering taking another A level, but no other subjects seem anywhat interesting to me, apart from A level Further Maths. My problem is in my sixth form you need an 8 in GCSE maths to do A level further maths, a requirement which I do not meet. I was thinking that I self cover some year 12 content during the space of the year, and then in the y12 summer holidays I can fully understand the year 12 further maths part of the A level and then try and do further maths with my sixth form for y13. Is this possible, or am I being delusional. For instance, I have done extremely well on my first set of assessments/mocks, receiving A* in all 3 subjects.

The vulnerable part of your plan is where you "then try and do further maths with my sixth form for y13". Only your sixth form can tell you if this is viable or not. How would your sixth form assess how well you'd picked-up Further Maths from self-study? Have they given you any indication that this is even an option?
Given that you've "done extremely well on my first set of assessments/mocks, receiving A* in all 3 subjects", have you tried approaching then now about this plan, to see whether they'd potentially be prepared to accept you joining Further Maths in Year 13?

It would be difficult (but not impossible) to cover the content alone but without teacher support and mock exams it would put you in a very sticky situation as doing a mock at home and at school where you are most likely gonna be sitting your final a-levels is very different. However if you have been achieved 3 A*s I think you could leverage that and ask your teacher to let you enrol in further maths since you obviously have a deep understanding of A-Level maths (proven by your A*) which is more impressive than the 8 you need at GCSE. I have a friend applying to LSE this year and he told me that doing further maths is very beneficial and they prefer that much more than other subjects since most of economics and finance is (in essence) money maths.
You could always take extra tuition and sit the further maths exam externally if you have the means and the time for that. But then again your best shot at this is asking the school if they could let you in.

yeah I was thinking about doing it externally aswell, but it would save me a lot of funds if my school allowed my to take the FM a level with them internally like everyone else.

can u not drop economic or business for further maths and try to convince them to let you do it despite ur 7 which i guess you have already tried. Were you planning on doing all 4 if they allowed it?