Thanks for that. Answering my own question I have found individual extra service stops
Kings Nympton - gap from Exeter direction, 18:08 to 22:16
Menheniot - gap from Plymouth direction, 19:02 to 22:08
Shipton - just five train a day including at 23:08 from Paddington
All seem sensible ways that give people an opportunity to get home to their smaller community after a night out.