Where did wartime Britain obtain aluminium?

Did Britain import bauxite or refined aluminium during the war?

Both, but the larger share was refined aluminium supplied through Canada.

The answer distinguishes bauxite or alumina from usable metal. Britain obtained some of both but relied mainly on refined aluminium that technically came through Canada. Norwegian output in the counterfactual would therefore supplement an established imperial supply rather than create Britain's aluminium access from nothing. The brief exchange does not offer a detailed tonnage breakdown.