Hi Stephen,
Thanks for coming by and I'm sorry to hear that you're still experiencing pictures problems on the TiVo® service.
I have taken a look at this and when I connected to the box remotely I was able to identify an issue with the downstream power level. This can cause/contribute to a problem with the picture pixelating or breaking up. To get this fixed I will be happy to arrange an engineer to call round for you.
I will pop all the details in a private message. Look for the envelope icon above in the right hand corner. 
Collette.
Tech fan? Have you read our Digital life blog yet? Check it out