Further update-
Selected Virgin channel 124 Gold, (Dad's Army of course) on main TV, perfect picture but no sound.
But In kitchen, perfect picture and full sound. ALL other channels are fine, just 124 on Tivo.
So connected HDMI direct to main tv -fine.
Swapped outputs from splitter, still no sound.
Instructions with splitter say with 2 1080 tvs put both scaler switches to on -done-no sound.
Turned switches to off in turn-#2 produces sound. So all ok but is the splitter at fault.?
Strange that only one of hundreds of channels only VM 124 is affected .
Any thoughts?