[JMT1985]

Heck, if they've reached the 1940s, wouldn't they lose some of the staff to conscription? You'd basically have to drop all of the male cast aged between 18 and 40 because they'd logically be off fighting in the war.

If you remember the second series, which focused on World War One, they had conscription there too - Thomas the footman off to war, but returned when he got him self injured on purpose - William the footman joins up only to get injured and the inevitable story ends - so they had done this before, so more conscription wouldn't be an issue for the plot.