Thanks for taking the trouble to research it, I wish it were so: Those small 3 pin plugs are used extensively in hotels for switched table lighting circuits, as are the old round pin 15 amp plugs for heavy duty floor polishers etc., as they are for stage lighting.
I had some at home for a circuit switching on four table lights at twilight, so I'm pretty sure that they aren't quite the same spacing. Funny, however, the BS546 spec. says the pins and spacing are the same.
Your research has pointed me in a direction: All I have to do is find someone in India or SA to send me a 2 pin line socket, if no-one here comes up with the goods!