Though I have few sources other than the excellent S. Howarth and D. Law's 'The Battle of the Atlantic 1939-1945: 50th Anniversary International Naval Conference', it does mention both U-Boat activity around, and ASW air patrols from, bases in South Africa. The focus was on the North Atlantic, but RAF patrols both to sight and then sink U-Boats became at least as important in the sea war by 1943 onwards. Despite the Suez Canal being an important supply route, the longer route via the Cape was safer through much of the war than passage through the Med, and so there were U-Boats deployed to harry merchants passing down the West African Coast, which necessitated the ASW infrastructure.

If he was aircrew, he may have been sent to South Africa for training- RAF recruits were sent all over the commonwealth and the USA. According to [this page from the South African Air Force] (http://www.af.mil.za/about_us/history.html) 33 347 aircrew were turned out by the Joint Air Training Scheme, the South African end of the operation.