The 'A' grade has been tragically marginalised, for GCSE purposes; the A*, on the other hand, has acquired a new significance in lieu of the devaluation of its A-Level counterpart. If you find yourself incapable of an arbitrary number (~5, with regard to the "better" institutions), then in all probability your application will be treated with as much disdain as that of someone who failed the very subjects in which you achieved 'A' grades; only having satisfied the baseline criteria for consideration (in terms of A*s) will they then look to your remaining grades, as a means to differentiate.
Of course, there are always exceptions: Mike (Onarmedbandit) has a U.C.L. offer, despite GCSEs which might be deemed by some to be below par for the course; although, of course, he's had a year out in which to improve his prospects (work experience, etcetera).