Before the war and during the war[WW2] it was blue suits or overalls.
In those days you had three blue suits . No 1's , best ,2's duty rig -red badges and 3's oldest blues red badges. Overalls were either worn over the blue suit or depending on climate on their own.
I don't think AWD [No 8's ]came in till about 1947 although the Canadians and US Navy had shirts and trousers working rigs.
Also you were issued with an Oilskin and an overcoat the pussers burberry
[raincoat] with detachable lining came in about 1956 .