I do CS at A level, and when looking at Unis I was surprised that nearly all don't require CS A level (lots did require maths). In the Subject Talks they explained that they pretty much start from the beginning, assuming everyone doesn't know anything about Computer Science. Obviously people who did CS will have an advantage, but I don't think you'll be the only one, though doing your own learning I think is a good idea, especially coding, as I honestly don't know how someone could go from non-coding to degree-level coding in a few months (I guess it apparently does happen though)