I'm told by Stephen Poppitt that he has developed this list after consulting with Keith Wickham (on behalf of BBC Archives), and Graeme Stevenson (on behalf of ORCA), and Derek Boyes (who conducted the Newspaper appeal for off-air recordings). It incorporates the database of theGBCC.info site, and that of RadioEchoes.com, and that of the YouTube account of Dermot A Maher.
This is the first time a comprehensive list of missing episodes has been published anywhere, to the best of my knowledge.
There are currently a confirmed total of 230 surviving episodes (including 15 tapes held by the BBC Sound Archive, 46 tapes held at BBC Manchester, and 154 BBC Transcription Service recordings at Perivale), 1 unconfirmed surviving episode, and 59 missing episodes.
A quick glance at The Clitheroe Kid fan-run website this week left me reeling from the good news. Well, a bit surprised to see yet more finds reported, anyway.
He's claiming that 235 episodes are believed to exist (if what BBC Archives say can be believed, and if the one unconfirmed episode he's been wittering on about for ages is ever found in Canada).
Apparantly a further 4 missing episodes have been found this year, in addition to a whole slew that came to light in 2018. So the known total, which IIRC was 120 episodes just 2 years ago, now stands at 235 (including 1 unconfirmed).
A list of the 56 episodes definitely missing is here (three more having turned up in the last 2 months) -
If you're not interested in a lot of detail, I can sum it up for you: one missing episode was rescued from a tape belonging to THAS (Tony Hancock soc), the contents of which tape were unknown because THAS didn't have a machine to play it on; and an old-radio fan named George Lane donated two lost episodes from a reel he found in 2016. And another enthusiast, this time a chap in Scotland, sent in an mp3 of a missing episode that he had made from a tape he's had since 1968!