A bodge maybe......
Channel 4 SD of freesat still seems to have a week of EPG so perhaps its only the over the air HD EPG is going.
Place the Ch4 SD nexct to you Ch4 Hd in your bouquet(s) to see whats on on the HD channel
To select an empty (of EPG) channel you also have to Menu -> Setup -> EPG -> Graphical Epg -> Skip empty services = no (do the same for any other EPG you may use)