Application advice needed

I got a 5 in GCSE Maths and I didn’t do pure maths at GCSE even though it was offered at my school. My GCSE grades were 9998885U, with a 9 in English and U in biology. I got an A* in A level Maths and Further Mathematics and an A in Economics, Accounting and Business. Will my GCSE math grade affect my application? And should I resit? I am looking forward to applying for Economics and Mathematics at LSE and Economics and Economics and Management at Oxbridge. Thanks very much for your time.