Ah yes, I have just looked at GrahamI's new photos. Common sense would have suggested looking at them before my last post! Never mind.
That loco with the visible flywheel in the side is a Deutz petrol loco. F & B had four of them, built in 1912, 13, plus another two built c1917. One was rebuilt into a battery loco by F & B, two were scrapped and one was transferred to Aberllefenni and was regauged.
Incidentally, the Ruston 177638 must have been filmed at Oakeley, as it wasn't transferred to F & B until sometime between 1953 and 1960.