Your qualifications don't matter very much at-all.
Your knowledge and analytical ability, that *may* be indicated by those qualifications matter a great deal.
So your GCSE maths grade really doesn't matter so long as you've got the standard employability 5Cs including Maths and English. But if you haven't got the basic grasp of maths and physics that sit around A-level standard, which is still a pretty low standard, you may have a problem.
So don't worry too much about your qualifications, do worry about your level of knowledge. But, whilst topping that up, you might as well get a few certificates to prove it.