Ah, problem solved.
We have a complicated set up in another part of the house with an Xbox and a 4-way Ethernet box and someone
had turned off the box!
But I am still puzzled that the 150 helpline continues to report the error
viz
"We are sorry that you are still experiencing intermittent problems with broadband and tv in the
[xxx] area"
It seemed too much of a coincidence which is why I thought the problem was at the Virgin end.
And there still remains the confusion that 150 says one thing and the service status checker says another.
But at least it's working again.
Thanks everyone for your help.