JImN,
Agree absolutely- although I continued to watch the later Avengers series too- always reckoned Patrick McNee must have been a lucky bloke to work with Honor Blackman, Diana Rigg, and Joanna Lumley! Wonderful beautiful talented cultured British ladies- what a late mate of mine used to describe inelegantly as "posh totty"......
I always preferred Jonny Dankworth's original theme too- I even worked it out on the guitar a few years back- lots of descending then ascending major sevenths in fast tempo...although the later Avengers theme music was a classy evocative piece of composition too.
There was indeed some terrific TV and film theme music back then from around late' 50's to mid '60's, on USA and UK films and TV shows- lots of jazzy stuff, and quite a lot of guitar led themes.
Route 66, Avengers, Naked City, Edgar Wallace Theatre (Man of Mystery) , spy and detective TV and films (Johnny Staccato, The Cheaters, Peter Gunn, etc) and of course all the westerns often with the main melody on electric guitar or 6 string bass/baritone guitar- Bonanza, Magnificent Seven...great stuff.
Back to Johnny, I saw he, Cleo and their bands three or four times here in Australia when they used to tour- they often set up a table in the theatre foyer after the concert, where they would meet and greet, autograph records, programmes etc- I even got to chat once to Cleo- lovely woman, and so talented- as was John of course, and their later bands included their son playing bass, so it was a family thing too.
I bet she misses John terribly- they were married in the late '50's I seem to recall- there was a bit of a stupid 1950s media controversy about it back then, because it was a "mixed marriage"- typical of the crap folks had to put up with back then.