Love On Wheels (1932, Jack Hulbert, Edmund Gwenn, Gordon Harker)

A musical with more bus sequences than 'Summer Holiday'! The titles include a stylised Green line coach:
Following this there is a line-up of eight Green Line T-class AEC Regals at Watford Leavesdon Road garage:
....and we see 1930-built rear-entrance T134 (GF218) being washed and prepared for a day's service, juxtaposed with domestic scenes:
There's also a quick shot of similar T113 (GF7280) being started up.
Once on the road there is much footage both inside and out of T134, running supposedly Bushey-Redhill-Croydon; included is a musical number sung by passengers and crew:
Also seen is this coach station, possibly the shortlived Poland Street Green Line coach station in London. New in 1930, it was closed in 1933. Another T-class is seen leaving alongside T134; this is a 1931 front-entrance coach. The footage is unclear but it appears to be on route D to Dorking.
The Duchess Street Underground Station is fictional:
There are also views of Metropolitan trams:
(Thanks Eric Scott, Dick Gilbert and Bob Martin)