For interest, it seems that the 1976 Peel session uploaded to youtube is the result of a rebroadcast in 2016. The relevant info is in following exchange, included among the comments section on the youtube page:
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Chris Brady
3 years ago
Please - are there any more John Peel sessions with Nic Jones around?

Sterling Cale
3 years ago
it seems his sessions are rare as Mr. Jones is reclusive. This set was aired on 6 Music, Boxing Day 2016, so it's tempting to think the BBC are plundering the archives and digitise the other seven sessions for future transmission.
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I do not know whether any more have materialised in high quality to date, however.

- Tony