EyeTV with either device described will get BBC HD and ITV HD (go to
http://www.avforums.com/forums/frees...eyetv-mac.html to get ITV HD working).
C4HD is trickier. The 310 with a Sky card in a dragon CAM might allow you to get this, but I don't want to comment further as A) I'm not sure it'll actually work and B) I don't want to upset the mods.