DickDastardly: It does seem that Sky are up to something stopping unused channels...
Some questions - how many channels of SD would have to be stopped to make space for an HD channel? I wonder if its 3? Please let it not be a compressed HD channel!
And please let it not be more paying sports channels - but as others have said something useful - like Discovery or Prime...
If a mux (half transponder) is converted to DVB-S2 H.264 then 9 or ten mpeg2 channels have to be reallocated. Four 1920x1080i channels or five 1440x1080i channels can be run on an S2 mux.