[Ed Storey]

Yes you are correct as there are indeed 3-round Thompson magazines in the two photographs and there is no disputing that 1SSF, a composite American special forces unit containing Canadians used 30-round magazines. But to answer your initial question did Commonwealth nations use the 30-round magazine then in the case of Canada, you need to find evidence, either a photograph or wartime document from Canadian sources to prove that particular magazine was used. If I were searching out the answer, then I would focus the hunt on I Canadian Corps as they fought in Italy where the Thompson was used.