I understand that these came from the collection of Graham Bruton, and are the only pre-1990 editions from the series that he has. There were 3 other editions of the same period aired on BBC 7 / Radio 4 Extra, but which are not included among them.
As I mentioned, these don't include the particular 1978 edition which David was enquiring about.
I listened to the whole of that long documentary on YouTube, which was interesting, and included lots that I never knew about the show. A 1990s documentary, in fact, hence made while the series was still in production.