Are you sure that you are actually on Virgin Media CABLE broadband and not the Virgin National product supplied down an ordinary BT phone line?
What do you get for the Host name from the following address?
http://cableforum.co.uk/board/misc.php?do=connection
Please exclude the first part of the address which will probably be an IP address.
Something like the following:
nn-nnn-nnn-nnn.cable.ubr04.livi.blueyonder.co.uk