Hey thanks for the reply Oliver.
A slight update - it transpires that they were with Talk Talk for a number of years and have been with Virgin Media for the last 12 months as they were offered a good deal on Internet, phone and TV. They are now wanting to move away from VM as the package is increasing quite a bit after the initial 12 months.
I guess they have been lucky to still have access to the mailbox after almost 12 months away.
They said they really want to keep the @TalkTalk email address so I've advised them to switch back to TT.