Hi Claire
The Exalls aren't my family: this was something I was researching for a friend - and I've forgotten most of it now! But I'll ask him if he knows anything about this, and get back to you.
I seem to remember, from researching a similar discovery in my own family, that the Canadian military records are pretty good and are on the Internet - I was able to find my relative and confirm that it was indeed him, because it gave his UK birthplace. Life's a bit hectic at present, but when I have chance, I'll see if I can find any urls for you.
Regards
Anne