Just seen in this month's HCC that there is a panasonic terrestrial digital tv decoder for £99 which has a RGB scart output - still don't think that it outputs DD or DTS. I'm not even sure whether its even possible to broadcast these audio formats at all.
As regards Sky, only a Sky+ box made by Pace outputs in Dolby Digital 5.1 and PCM stereo via optical out. There are quit a few films on Sky premier and Box Office broadcast in DD5.1 now. Sony digiboxes also have optical out, however, Sky have disable Dobly Digital 5.1 and it only outputs PCM stereo.