1953's only five years after nationalisation so many, many wagons, many coaches and quite a few locomotives would have retained earlier liveries. A number of locos would, indeed, have the full 'BRITISH AIRWAYS' inscription. Few wagons would have retained pre'36 liveries though ............... and one variant you don't mention is former PO wagons - mainly 12-tonners by then - with 'P' prefix numbers. Livery-wise it's a complex period ........ and very fascinating !