I found this the other day: "a scale diagram of current popular British printing papers, excluding ledger papers etc". Current means 1968. It was from an article about the arrival of metric measures in the printing industry.
I vaguely remember talk of Quad Crowns and the like in media and production chat when I was a junior media-buyer booking poster campaigns. You can see why metrification would see sensible but it would be nice to see Double Oblong Foolscap as drop-down option on your printer menu.