Canadian here.
The UK use of the word "homely" always gives me pause because to me it means plain and ugly. Also "half six" for 6:30 confuses me for a second.
My British born and raised DH is a high school teacher and he always gets laughter when he calls an eraser a "rubber".
Another one I have to translate in my head is "pavement." We call it a sidewalk.
We sometimes call the sea or ocean the "salt chuck." Then there is tuque, which is a knitted hat.
We have a "hydro bill" instead of electric bill.
And I know a person is a fellow Canadian the minute they ask where the "washroom" is. Equally, an American will say "restroom."
"Swimming costume" sounds very quaint to me. It's a bathing suit here!
I had never heard of a gilet until a British family member called a puffy vest a gilet.