You could give the A+ Certification a shot?
It costs about £500 for the course here, but i just entered myself for the exam only (can't remember how much, but it was fairly cheap - when you think about the half grand you save) and bought a couple of revision guides to see what sort of stuff they ask, most of it is fairly basic hardware/troubleshooting stuff, but i think it's fairly well recognised.
I did GNVQ Intermediate ICT with my GCSE's - it was a complete waste of time. We spent ages and ages screenshot'ing excel spreadsheets/access databases, etc. In my opinion, it's not really worth the amount of work you have to put in (besides the fact that you can get up to four A's for a distinction). From what you've said about your experience with PC's, unless you really do need a general ICT qualification, then i wouldn't bother.