the fact they used that way too modern railway carriage at the end that broke the reality for me. Surely they could have at least fitted some old leather seats.
Leather seats not used in UK railway carriages since the 19th Century and rarely then.
The carriages used in the movie are 1950s era stock, not a world away from what would have been in use in 1940, but the correct stock would also have been available to the filmmakers.