I took 7 of my GCSEs early (Bio, Chem, Physics, Maths, English Lang, English Lit and French) and didn't do very well (1A*4A2B) which was much lower than I was capable of. The Chem and Physics were IGCSE though which I think was partly responsible for the Bs ( i was looking at past papers a few weeks ago and they were harder than most of my OCR A2 papers!).
I meant to go on and take 2 or 3 more GCSEs mixed with a couple of AS levels the year after but I switched schools and that wasn't possible there. I just started my AS courses which has really messed me up long term - 7GCSEs isnt really enough for uni esp with the grades I got and no one actually cares it was a year early. I've just finished my A2s now and I'm not sure whether to enroll somewhere to sit more GCSEs just so I can put down I have them. It seems stupid since they're so easy and I'm now 17 but it's just one of the hoops people have to jump through!