Turned out to be cabling problems. Virgin media engineer was very professional and painstakingly hunted down the problem.
Turned out to be the cable from the old master socket (downstairs) to upstairs router.
On a temporary basis, having to run a 10 metre extension lead from upstairs to downstairs, until I can get an electrician to sort the cabling out.
Only issue I have is it worked perfectly prior to conversion to digital. New digital system must be less fault tolerant
Many thanks for all the assistance from this forum.