This website is a photo tribute to the 21st Battalion CEF that formed in Kingston Ontario in 1914 and proceeded first to England, then on to France to fight in the Great War.
There's a lot to read on this site, including the transcription of the diary of Company Sergeant Major Lou Verdon.
He is perhaps an extreme example of a recent British immigrant who signed up early in the war. Born in Cheshunt, Hertfordshire, England, he came to Canada in July 1914. He had a police background, stayed initially with his brother in Ottawa, joined the Dominion Police and the Governor General's Footguards. By 6 November he was attested to the 21st Battalion at Kingston Ontario and, less than a year after he left, was back in England as a member of the CEF.