(BBC documentary, 1972)
Betjeman is more often associated with railways, but this filmed essay features fragments of a good many buses.

Southdown Leyland Leopards and a 'Queen Mary' Leyland Titan PD3/4 open topper:

New to Brighton Hove and District (42), Southdown FS2042 (XPM42) carries Southdown BH&D fleetnames. It's a convertible Bristol FS6G/Eastern Coachworks seen here in open top guise:

Looks like Van Hool bodywork: