Most Unis don't actually require Computer Science for their degree courses, only maths at most, except may the best of the best.
I'm in Y13 currently also going for a degree in Comp Sci, so I can't speak for if when you actually get to the degree it is important to have A Level Comp Sci, but most unis seem to base their Y1 modules around learning the basics of Comp Sci so you may be fine without.