Hi All
Just an update in case someone has the same issue and wondering how to cure it.
Basically you need VM technician come down and sort it out.
He basically said it could have been anything so the first thing he did was to check the isolator, the little box that connects the wire coming from the outside to the wire inside. Apparently it was very old so he swapped that for a new one. The inside wire goes into a splitter where with one wire turns into two, one going to the tv and one to the wifi router. He changed these two wires as he said they looked like something not supplied by virgin, which I can concur.
When that was done, hey presto BBC channels returned.
So it could have been the isolator or damaged wires.
Thanks all for your help especially japitts.
A big thank you to the VM technician who was extremely efficient and was in and out in less than 20 minutes .... brilliant.