Well, thanks for the warnings.
I'm going to stick with Virgin for the time being anyway, I checked their own website yesterday and discovered they now do 1Meg for what I'm paying ... I sent them a slightly miffed email complaining that I'm still getting 512k for the same price. They said they were doing phased free upgrades, which is why I've not been done yet ... and then initiated the speed upgrade on my account. Yay!