A-level maths for finance

Hi, I am interested in pursuing a career in finance however, I’m worried that I will not be able to achieve a finance degree as I’m not terrible at maths but not amazingly great, will I be able to improve?

You should be able to improve, depending on how you revise. Have you looked at videos offering tips on how to improve on your grade in maths? See the following for example:
https://www.youtube.com/watch?v=1wbz3CST8Vg
https://www.youtube.com/watch?v=CeAaACKEiHo
https://www.youtube.com/watch?v=--gViX-erOs
https://www.youtube.com/watch?v=l3ctFrUX9iM
https://www.youtube.com/watch?v=ixf8RJp8H1s
https://www.youtube.com/watch?v=mrnUDXvfMCM
https://www.youtube.com/watch?v=3dJqheOpRDE
https://www.youtube.com/watch?v=pM0_0E3sV-8
https://www.youtube.com/watch?v=MNDpM4G8D68
There are other videos, and the above is just from the first page of Google.
On the other hand, which specific role do you intend to go into? Finance doesn't just have one role, and each role have their own specific requirements.
Do also note, there's no single role in finance ever asking you for a degree in finance. In fact, a lot of the people in finance don't have degrees in finance and have either no degree or degree in any random subject with no relevance to finance. If you don't intend to go into financial research in academia, you won't really specifically need a degree in finance.

Thank you for the info! I’ve been looking at the role of a financial analyst

When people say financial analyst, they either mean someone who recommendations for investment decisions (investment analyst) or someone who helps with making recommendations to improve financial performance of a company (financial analyst).
See the following:
Investment analyst
https://www.prospects.ac.uk/job-profiles/investment-analyst
https://www.investopedia.com/articles/financial-advisors/121515/investment-analyst-job-description-average-salary.asp
https://nationalcareers.service.gov.uk/job-profiles/investment-analyst
https://www.cfainstitute.org/en/programs/cfa/charterholder-careers/roles/financial-analyst
https://www.forbes.com/advisor/education/business-and-marketing/financial-analyst-job-description/
Financial analyst
https://www.accaglobal.com/gb/en/study-with-acca/your-career/sectors-industries-roles/financial-analyst.html
https://jobs.icaew.com/article/financial-analyst-job-description (ignore information about MBA and degrees)
As I am not entirely sure which of the 2 you meant, can you clarify so I can make the appropriate recommendation?

Thank you for the reply! Sorry to not clarify beforehand, I did mean the 2nd link, financial analyst

Then you should be looking to do an accounting qualification.
Professional accounting qualifications don't require you to have A Levels in specific subjects prior to applying. Most are fine with a few passes at A Level and a few GCSEs above Grade 4; one doesn't require you to have any prior qualifications, not even GCSEs. This is irrespective of whichever degree you choose, because they only care about your A Level and GCSE grades.
Should for any random reason you decide to do a degree in accounting, accounting degrees generally don't require any specific A Levels generally. Those that do usually ask for A Level Maths, but that's because it's because it's a joint degree in finance and there are the more quantitative finance modules (some joint accounting and finance degrees don't require you to have specific A Level subjects). With the degree, you should be able to claim up to exemptions from 9 papers (should you pick specific modules in your degree). However, the accounting related degree won't make you preferred over job applicants with degrees in other subjects or candidates with just A Levels and GCSEs for job applications.
So no, you won't need A Level Maths. It's nice that you do have it, but it's not the end of the world if you don't. What's more important is picking the right professional accounting qualification after your degree or A Level. (I recommend picking the qualification after you get your entry level job, since you can check what professional body your line manager (or another fully qualified accountant in the firm) is qualified under - you would need recognised professional work experience to fully qualify for your chosen professional accounting qualification.)
Note: I recommend ACA as opposed to ACCA and CIMA, because you can pivot to another accounting related role and it's the most well regarded qualification in the country. For international opportunities ACCA would involve the least paperwork, but transferring using ACA in countries where it's recognised also allows you to get the most well regarded local equivalent as well. Having said that, there is nothing to say that you can't switch to other accounting qualifications later by doing extra papers and claiming exemptions using your completed accounting qualification.