I'm very sorry for the problems you're experiencing with your TV service at the moment, I've located your account to take a closer look and I can see you've recently had an engineer out to take a closer look.
I hope that means things are now working as they should? If not, get in touch and I'll do what I can to help.
I am having similar problems with our v6. Most of the time it's fine, but now and again the screen will glitch and flicker with both picture and sound affected. Sometimes the screen goes completely black for about 1-2 seconds. This can happen with live transmissions as well as when watching recordings. I found that putting the v6 in to standby and turning back on resolves it. Doesn't appear to matter what channel I have selected either.