The GCSE criteria is the first 5 at A-C including English and Maths. Straight Cs is acceptable although As is better.
As important it the next qualification and that is 2 A levels.
All you are required to do is meet the minimum criteria. As long as you meet the minimums then you will have a chance to show how you can meet the aptitude and personal qualifications at interview and during the tests.
Work hard; no sweat.