D-Day Minus One (1945, USAF)

A 16 minute record of the operations of the U.S. 82nd and 101st Airborne Divisions in the 1944 invasion of France, has scenes of the troops being ferried to their camps in England in buses, at least two of them from Barton Transport. The screen captures are from the public domain copy downloadable from http://www.archive.org - the original film would no doubt be clearer.
This may have fleet number 331, if so I would guess it's Barton 331 (DVO117), a 1938 Lion LT7/Duple:

This Barton Leyland is the most clearly seen; I believe this is 252 (BVO452), a 1936 Lion LT7/Duple: