Ok - so I broke off my 40 minute wait on 150 to dial the 0800 number and discover there are no local faults. Which I'd guessed as neighbours on either side have no problems and mine only started after speaking to the rep who activated my second box this morning.
Long story short: I had a virgin media account at this address a few years ago. I moved away and recently returned, setting up a new account. Now I am unable to set up a myvirginmedia account (a ticket has been raised for this problem)