On the other hand, in 2005 he played to a full house in Jazz Britannia at The Barbican, with his big band and in the small group. The BBC show I witnessed was a full house too.
Local Sunday pub lunch gigs on home turf I would suggest, maybe aren’t representative of the full picture. Similarly, I saw Mike Westbrook playing to less than 10 people over the past year at a small venue, yet he had packed houses at Ronnie Scott’s recently.
There’s no doubt that his profile dropped big time in the 80s and I recall only that Hep LP with Don Weller coming out at that time. Maybe his bio will shine some light on this but the sale of Argo to Polydor caused quite a bit of grief in the late 70s and maybe this led to a lowering of profile in terms of recording. As the bio makes clear though, he was extremely active, including involvement in youth music education.