Searching through my collection I also find
British:
Agatha Christie: Poirot (1989-2013)(13 seasons+CS)(Acorn Media) Note probably only the first 6 seasons are before the end of the 20th century
House of Cards (3 seasons+cs) (BBC)
Smiley's People (Mini series)(Acorn Media)
The Avengers (the British TV series not MARVEL) Has Two seasons available for region A. Essentially the Emma Peel years. I have all the available seasons (season one only has some episodes available), but I believe the other seasons are Region B locked (I haven't tested them for region A).