I got my connection back last night, thanks in no small part to James Bailey, so a big thanks to him for his help!
Heres the thing though, I had been disconnected for 3 weeks and do you know what was stopping me from disconnecting??
My username!! Now, I should stress that I had made NO changes to this myself prior to loosing my connection, so it wasn't me being a numpty!! Something about the transfer to LLU obviously caused a problem. However, I don't know whether it was the process of me running the connection tests, or something that happened automatically at Tiscali/PN that caused the change in my username settings. This is what appears to have caused the protracted delay.
So, if any of you are stilll disconnected make sure your modem isn't just trying to log you on as just your username, it should be [your user name]@plusdsl.net.
Sorry if this is blindingly obvious to some, but this very simple error appears to have just caused me a lot of unecessary downtime!!
BTW Now its working I'm getting 8064 downstream and 680 (I think) upstream, so no probs with the speed as far as I'm aware