With the last few days news I'm now almost certain Virgin have done a trial, I do seem to remember a friend kept getting a reference to sysip, which if I remember right is a phorm domain. I was digging on the net to see if I could find any references to it on the VM network, I've had no luck so far but this forum has someone reporting a sysip problem on BT on June 28, which I think must be last year rather than 2006
http://hubbub.labs.bt.com/?pagename=viewpost&id=24712
also found something here relating to 2006/ 2007
http://forum.utorrent.com/viewtopic.php?id=25456
http://forums.digitalpoint.com/showthread.php?t=152409