Currently sky have most of their channels encoded at 544x576 with a low mpeg bitrate of around 3mbps which is the reason for blurred pictures and pixilated frames in fast motion scenes. 544x576 is ok for most 4:3 channels displayed on a 4:3 tv, but definately not ok for 16:9 channels pan scanned on a 4:3 tv where the sides are cut off to centre the picture, watching a 16:9 channel encoded at 544x576 pixels on a 4:3 tv with panscan enbled is like watching an old VHS tape, its worse than watching an analogue freetoair channel. Sky sport 1, 2, and 3, all movie chans inc box office but except for tcm and mgm are all encoded at 720x576 16:9, tcm and mgm are both 544x576. the audio bitrates on the box office channels are 160kbps 4800khz, sky sport 1 is 265kbps 4800Khz, cant remember off the top of my head what sky sports 2 and 3 are, i think 192kbps 4800Khz. sky movies 1 and 2 and sm greats are 256kbps 4800Khz. But surprisingly Sky Digital Music is all 192kb/s 3200Khz and not 4800Khz, u can definately hear the difference in quality, well I can! why the low sample rate sky? why not just use 4800khz? its not like audio streams take up much bandwidth anyway, increasing the 3200Khz to 4800Khz will not use very much at all. The Preview channel has the lowest resolution 480x576 16:9, just have a loot at Preview and compare it with other channels, the picture is blurred and not very clear compared to others.
Recently sky changed the resolution on a few channels, nat geo, uktv from 544x576 16:9 to 720x576 16:9, and BBC from 544x576 16:9 to 704x576 16:9, I watch natgeo a lot and noticed the difference in quality straight away.
C4 is also 544x576 16:9, i never watch C4 on sky i watch the freeview feed which is 720x576 16:9