I presume the schedule was brought forward as maybe there was a Jimmy Savile episode they couldn't show.
Anyway this episode is repeated on Sat night / Sun Morning - BBC4 - 1am (if you look at the info about this on the Sky Planner it is not correct, as it still shows the episode they have pulled).
Look out for Dave and Jim's disappearing microphone....
I went to the BBC in 1977 and tried my hardest to get in to the recording. My blagging didn't work - I had to be satisfied with meeting the band at the gates on their way out.