As you say, most likely this is a low bit rate or MPEG encoding issue. It's not a resolution or SD v HD issue.
Looking at data flowing through the router all the Sky Sports channels use 2.5Mbps, or as close to that as my crude measurement allows. That hasn't changed recently. Note Sky Sports 1 doesn't have a higher bit rate.
I think I read a while back encoding is H.264. I think I'd expect better than we see at 2.5Mbps.
It feels like the picture quality has degraded recently but I can't be sure. Recent cricket has suffered badly from compression artifacts.
Would be nice to have a higher bit rate but then TalkTalk may have to up their current 5Mbps threshold for access to the multicast channels which would upset others.
OCEs: Any chance of a guest appearance from a techie to throw some light on what we're seeing?
Happy New Year one and all!