now I am crazy.
I managed to revert back to a system checkpoint I had before I started changing stuff.
Guess what, TV record now works perfectly

.
Right now I need to sleep. Between thinking about blotchy screens, colour depth, learning XP and playing with sound cards, my brain hurts - too much information.
Bottom line for me is when I revert to this pristine state, my screen is perfect - no blotchy effect or colour banding, no dead pixels, TV record works, great sound - in a word, the whole system is perfect. Now all I have to do is work out what is going on with everybody else's system.
Driver hell IMHO.