Another update.
Finally received some correspondence (of sorts) from Virgin Media today. They have sent the update letter to my previous address, despite them apparently having my new address, as this was given to them when I moved as they informed me that they would be unable to transfer my service to my new address as Virgin Media was not available at that postcode.
So, they have obviously been sending all correspondence to the address that I had told them I was no longer living at.
The mystery continues. Have passed details onto my legal adviser and will now look into the next move.