Heya! I did 5 A-Levels, and although it was a lot of hard work, I was really pleased I did it. I did loads of extracurricular stuff too, so was really, really busy. However, if you've got the motivation and want to go for it, then jump right in. At the end of the day, if you're finding it tough after the first year, then you can always drop one. If you've already done a lot of the ICT course already though, I don't see you'll find it much of a problem. I found Chemistry my hardest A-Level by far, but.. personal preferences etc...
Trying to think of any other advice I could give... I think at the end of the day, you should go for it - if you don't, you might regret it and you can always drop one if you're finding it too much.
Did you find it reasonably ok to get those grades at GCSE or did you really have to work for them?