Okay well I thought I'd post saying I've just received some excellent service from VirginMedia.
Phoned them up on Monday to tell them my internet was really slow (speed tests showing 7.5Mb DL and 0.001 Mb UL!). Virgin were showing packets being lost to my modem and so they sent an engineer out.
The engineer arrived today, swapped my modem out and hey presto I'm running at:
So hats off to Virgin I say!