It's Not Cricket (1949 film) - Wikipedia

1hr 17mins
Dirs: Alfred Roome and Roy Rich
Starring: Basil Radford and Naunton Wayne

Kicked out of Army Intelligence, a pair of upper class twits set up as private detectives

This good, fast-paced, comedy is one of the most highly regarded of the period and has a very strong cast for what was essentially a low-budget B movie. It features early scenes filmed at a port with the central characters boarding a boat train to London. It is not known exactly where this was filmed, but it isn’t ‘Folkestone Harbour’ as denoted by a signboard in the background of one shot. Some of the coaching stock present is the Continental Stock, built by the Southern Railway to a SECR design. The coaches had matchboard lower sides, Pullman gangways and buckeye couplers, as well as inward opening end doors, and some lasted in traffic into the 1960s. In the background to one shot, a rake of Southern Railway suburban stock is also visible.

Stood on the ‘platform’ at the port, Edward Lexy buys a newspaper. The banner repeater to his right is clearly of railway origin.
This is a good and rather rare shot of the unusual Continental boat train stock in Southern Railway livery. Did this stock stick to a particular route that might help narrow down a location?
Maurice Denham leaves a station. Don’t be fooled by the signboard propped against the bridge, this is not Folkestone Harbour, and it may not even be a station. (Thanks again to reelstreets).