I grew up in Blackpool,during ww2 many radio ops were trained in the town.Above the Burtons tailors shop was a big room used for final tests. I always thought that if they failed then they had gone for a Burton.
It seems there are many other expalnations.

This is the reason for the expression I’ve seen too. I can not find it at the moment, but somewhere in my collection of books I’ve got the autobiography of an RAF wireless operator, and he was trained above that Burtons tailor shop in Blackpool. From memory, he said that those who failed their tests had to go through the tailor shop on the way out and not through the normal exit from the training room. The reason being that it was considered bad for the morale of guys waiting outside the room for their test, to see how many failed! That was the reason this W/O gave for the exression, but like you say scotavia, it seems there are many more.