As well as InterCity's above-mentioned charter division (and dedicated stock), BR used to run "Merrynaker" excursions, from various routes to popular destinations. The stock was usually a rake of Mk1s including rudimentary catering - and invariably there was a trade stand (books, etc) in the brake van's cage.
As a lad, I still recall my parents taking me on such a trip - up the Midland Main Line then across to Blackpool. It was 1983 and, goodness knows why, I still recall the loco was 45003.
Private enterprises also chartered BR stock and, as well as those mentioned above, the early-mid 1980s had F&W (John Farrow and Peter Watts, who subsequently established their Hertfordshire Railtours and Pathfinder Tours), the Branchline Society, plus specialist clubs such as Class 40 Appeal, Class 20 Loco Society.
Aha our posts crossed in the post!