guys, if you want to know if it's good enough for cambridge/oxford or any other university, just check the course on their website and what their GCSE requirements are. It depends on what subject you want to do.
For example, the average proportion of A*'s at GCSE for an average medicine candidate at oxford and cambridge is 90%.
Cambridge look mostly at the UMS attained at AS level (usually they want around 93-95% in the 4 subjects) as well as good GCSE's. Oxford don't look at UMS but more at GCSE's, I don't know the specific minimum amount of A's needed but look for it yourselves.
If you want to apply to a certain course, you should have at least the energy to look at the requirements. This will also allow you to gauge how much work you need to put in right now and not leave it 'til the end of the year and find out that you can't apply because your AS levels/GCSE's were not good enough.
This is not to discourage you as these are MINIMUM requirements, because candidates with lower amounts of A*'s have got in but that is because their AS level grades allowed them to be accepted AND also personal statements AND entrance tests AND interview. btw still talking about medicine. other courses want different requirements - look them up!
Basically, what I'm trying to say is that GCSE's are not the sole factor for getting into university. They are just a minimum requirement. In a few months time, no one will really care about what you got at GCSE, so long as you meet the MINIMUM requirements (e.g. 3 A's in sciences and A in eng lang for X course at Y university).
I would say that AS levels are a VERY IMPORTANT factor for university applications so make sure you work hard for those so that you can get predicted high A2 grades, with which, the uni's are more likely to select you.