I knew it was coming, but didn't know exactly when...
Virgin Media are in the process of transferring the account to myself, part of which involves temporarily switching off the broadband connection, whilst they then setup a new connection in the new account holder's name.
Fortunately their Customer Services are very helpful and knowledgeable - who during the first call confirmed that the broadband had been disconnected. The second call involved them updating the information for the cable modem, which required the MAC address.
So, everything is up and running again and the back-log of my emails are slowly creeping in. We're going to upgrade the account soon to the triple XL, which includes 20MB broadband amongst others. I'll let you know if doubling the speed makes any noticable difference.