Do grades matter more than skill?

I'm taking 4 A-Levels (Maths, Further Maths, Physics and Computer Science) and despite the fact that I enjoy them all and I'm quite good at them all, I think I'll probably get an A*AAA. I know that the entry requirements are usually A*A*A for Computer Science but I've also got a decent portfolio under my belt of games and other such projects. Will these projects have any impact on the application process or are they simply an additive to heighten the chances of an interview?

We need to be confident that you are capable of hitting required levels in public examinations at the end of your schooling as our extensive research has shown that the better students do in these the more likely they are to do well in Cambridge and, vice versa, if they perform less well then they are likely to do less well at Cambridge. We do take other things into account, including super-curricular exploration of the subject, which is why we do not simply admit on the basis of exam grades alone but the offer levels are where they are for a reason in that we regard that as the minimum level necessary to do well at Cambridge.

Neither Oxford or Cambridge allow extra-curricular activities to influence the decision surrounding your application.

Of course, it looks good for you to have done extra projects, but it will not have a discernible impact on your offer. If you do not meet the entry requirements, no amount of extra projects will change their decision.

Cambridge require A*A*A for Computer Science, but Oxford only require A*AA, with the A* in Maths, FM, or Computing / Computer Science - so you meet their requirements.