Another update on the sound bar saga. I had a different problem, namely recordings stuttered and froze when being played. Someone at VM downloaded some software and said if that didn't fix it to switch the box off and on again (the cure for all ills). So on Thursday morning I tried. The off bit went OK but the on bit failed, it appeared to be in a loop downloading the same bit of software over and over again but never getting the box to restart.
So they sent me a new box, the third since all this started in January. Arrived late yesterday and I installed it this morning. Recordings seem to be OK based on a limited test.
The reason for this missive. I can now control the volume of my sound bar from the VM remote even though I am still using a digital audio cable. I wonder if VM know they have fixed this? Anyway let's be thankful for small victories.