Brits and Canadians in the Spanish Civil War

The (UK) National Archives is marking the 75th anniversary of the outbreak of the Spanish Civil War by adding records to Documents Online.
More than 4,000 volunteers who left Britain to join the International Brigades fighting in Spain are recorded in Security Service (KV) files, now online and available without charge until 27 July 2011.
TNA has more information at http://www.nationalarchives.gov.uk/news/591.htm
The war, often seen as a proxy fight between Fascism and Communism, had no official involvement of governments in Canada or the UK. Canada discouraged participation, including by passing the Foreign Enlistment Act in 1937. Canada was concerned about domestic Communist insurgency. Many if not most of those who enlisted in the Canadian Mackenzie-Papineau (Mac-Pap) Battalion where anti-Fascist rather than Communist.
A national monument to the Mac-Pap veterans includes the names of 1,546 Canadians who served in Spain. A simple list is here.
The book Renegades: Canadians in the Spanish Civil War, by Michael Petrou has an appendix with name, home(s), ethnicity, date of birth, occupation and final status. Petrou gives statistics showing that of those for whom ethnicity is known 100 were English, 69 Scottish, 42 Irish and 6 Welsh. 
The LAC catalogue lists several hundred items, mainly photographs, from the Mac-Pap Battalion.