(Channel 4 mini series, 1992) Based on a Mary Wesley novel and following a family from 1939 to the 1990s.
Episode 3:
This bus appears in a scene set in the early days of the Second World War. It's in allover grey with no destination blinds, and it's clearly a postwar Leyland RTL. However, the registration it carries appears to be DLU347, which would belong to a prewar (1937) all-Leyland Titan TD4, STD37: