Many thanks for getting back to me.
I am, unfortunately very used to the 'usual and normal' recommended steps to try and address this issue as it has been a constant 'pain' for the last 3yrs +.
It varies between the odd pixilation along the bottom third of the screen, to flat out double images, full screen pixilation, picture 'lag' (some times for 1 - 3 sec) until it all gets so bad I switch it off. It occurs on most channels but is particularly bad on ITV, Chan 4, BBC1, 2, and gets much worse after 17:00 most evenings and even worse at weekends.
Without a doubt I am convinced it is the, now aging TIVO box (the original type). I know it is not the same thing but, a free sat box does not seem to get effected.
I even tried to upgrade to the latest TIVO + Hub but Virgin didn't seem to understand what I wanted and sent just a new Hub2 instead (which is now fitted with no difference to the picture).
I no longer have a main external terrestrial arial so am reliant of the cable for TV and cannot compare quality.
Any suggestions ?