I've noticed recently that BBC2 HD and SKY1 HD have become unwatchable (pixelation, stuttering and freezing). I've tried rebooting and running the suggested test from my computer but this doesn't do anything. SD versions are fine, this occurs on both my boxes; TiVo and V+ HD.
Sky1 HD has never been particularly stable but BBC2 HD has in the past been fine. Haven't noticed any other HD channels that I watch behaving like this. I'm in the Dartford area - no known problems that cover this under Service Status & Faults.