Thanks again for your help.
I found Oliver & Harold 1926. Harold must have gone to Canada (the first time) between 1911, when he was living in Impington, and when he returned to England with the Canadians in WW1. He presumably stayed until 1926 when he went back to Canada with his brother.
I foundOliver's marriage, and their son David, but I couldn't find the record of Guy retuning in 1935.
Bob