Yeah, seems it was my mistake
You just log into mypipex, go to 'upgrade account' in the CP, choose 1 meg if your on 512, check in the pricing box below and the cost will be exactly the same, except you'l have a regrade fee (of £15inc) ...
7-10 Working days is the quote, there was quite a few problems with it at the start, with people being charged the regrade fee incorrectly (15ex VAT, 17£ inc).. which isn't too bad, they sorted that out. The major problem was BT put a halt on the process, which I believe is ironed now and upgrades are taking place. Some people have been upgraded 2-3 days after the request.
What's £15 for a better service, and Pipex seem to be on top of everything
I'l let you know how it goes.