(1949, Stanley Holloway et al)

A number of London Transport types of the period are seen, including RTs, STLs, LTs.

One STL is STL446 (AYV604), a 1934 AEC Regent with LPTB body rebuilt in 1948, possibly after the film was shot.

Two earlier STLs are STL31 (JJ4343), an AEC Regent/LGOC new to London General in 1933, and STL189 (AGX527), a Regent/LGOC new to London Transport later in 1933. Both were transferred to London Transport's Special Events fleet in 1948 and withdrawn for scrap at the end of that year.
STL31 is seen here with a similar bus behind, and behind that a T-class AEC Regal:

This is STL189:

It's not possible to tell whether this is STL31 or its twin:

Seen twice is this 1948 AEC Regal III/Strachan, SMY254, operated by Wright Brothers of Hanwell, with 'Relief' boards in the windows. Wrights had three of these, and SMY253 and 255 are recorded as hired in by London Transport between 1947 and 1949 to help with vehicle shortages, so it's quite possible that 254 also performed in this role:

Another AEC Regal/Harrington, HYN543, of Rickards:

….also a six wheel Albion Valkyrie saloon; Bob Wingrove identifies this as 1938-built XS4765 as this was owned by Ansell's Coaches of Camberwell. It was ex Youngs of Paisley, and operated for Ansell in Young's livery. It had a Cowieson body:

Another is this passing coach:

…and a T-class AEC Regal/Weymann: