Thanks for the info. I called to report the fault this morning and was told the same thing.
I did suspect this was the result of the "upgrade" work Virgin notified us was taking place on Monday 7th. The notification the following day that it was now "All Sorted" was obviously an auto email, as something had clearly gone wrong the previous day.
The annoying pixellation issues returned well before last week, but nothing as bad as this.
I am hoping that when the area issue is resolved, it may improve our TV picture issues that have been ongoing for years.
However, there may still be an underlying signal strength issue as the box in the bedroom, which is usually fine, is affected to a lesser degree. The TV picture from the box in the living room is much worse, but runs from a splitter with the hub. This would suggest, to me at least, that there is a signal strength issue with the box in the living room.
When picture break up is evident in the living room, 99% of the time the picture from the box in the bedroom is perfect and it has a seperate line into the property. Maybe that's what I need for the Tivo box in the living room.