Don't underestimate the issue of capacity. Yes, the major schools will have chucked out a few pupils who failed to obtain adequate GCSE's, but there is usually a very strict cap on numbers, and plenty of people will have expressed interest in being considered as candidates, and at a far earlier stage.
Ability-wise, all sounds fine. You have to interview well, so raise some interesting questions (that can't be answered by studying the prospectus).