Recalling Murder by Decree made me think of the film series that BBC2 used to show in the 70s and 80s in the 6pm slot.
On a number of occasions they showed the 14 Basil Rathbone Sherlock Holmes films he made with Nigel Bruce. I remember them being screened on Friday nights at 6pm between September and December in 1976 or 1977, then at least once in the 1980s, and probably more than once.
The 12 Johnny Weissmuller Tarzan films got the same treatment, 6pm on Fridays between September and December, and I recall seeing them sometime in the early 80s in particular. They also did the same with the later Tarzan films of Jock Mahoney and Mike Henry, 6pm on Fridays between September and December, maybe also including the Gordon Scott films as well.
Finally, several times BBC2 showed the Fu Manchu films made by Harry Alan Towers in the mid-late 60s with Christopher Lee. Now, I believe these were shown on Wednesdays at 6pm, maybe in the summer, and I can't recall if all 5 were screened or if the final 2 Jess Franco ones were omitted. They were shown in the late 80s at least, and I still have a couple of them that I recorded on video tape at the time.