Will I have a chance in getting accepted in a top uni

You’d have to look at the universities individually to see what their requirements are. I don’t know much about LSE, but I do know that Cambridge has a more hollistic approach to applications, so your GCSE grades may not the be all and end all, but Oxford really do place a heavy weight on GCSEs, so you chances may be smaller. If you were to choose one of the two, Cam would likely be your safer option, but I’m sure you don’t need me to tell you that economics is a really competitive subject, especially at Oxbridge.
Just make sure when you do apply that you apply to a couple ‘lower’ ranked unis, that have lower entry requirements/may not mind so much about your GCSEs being all 8’s and 9’s etc. Your English and maths GCSE grades are a 6 or over, so that will work in your favour too. Good luck

I didnt too well in my gcse's (6 7s and 4 6s) which most likely below average for a typical oxbridge/lse etc student
I do maths futher maths economics and chemistry for A-levels and i sit the maths exam this year (year 12) and the rest in year 13, if i do get an A* in my maths a level will this give me any hope in getting accepted (for economics) at a top uni?
(assuming my predicted grades, personal statement and admission test is around/above average to a typical top uni applicant)

LSE focusses a lot of personal statement so if this is good then you have a chance.