It's almost too simple and thus often overlooked during a rebuild. Camshaft bearings are pressed into the block and thus are usually done by a machine shop. You would not rebuild an engine without replacing the rod bearings, so why not the cam bearings? Two sizes of cam bearings; blocks with tappet covers use VPC956, those without tappet covers (eg, Austin America) use VPC989.
Sprite , Midget and Morris Minors have the same block as the Mini, thus these same cam bearings.