Well, my reasonable connection speeds have now disappeared and I'm worse off than before. Speed is now around 1Mb. If it's still the same in the morning then I'll be calling tech support. After that I expect I'll be talking to customer services and downgrading to 1Mb until I hear that the problems have been resolved.
Yesterday I thought there was some light at the end of the tunnel, however it turned out it was just some b*****d holding a torch