2-pin low-current [5A max] unpolarised outlets would be useful. Kinda like a slimmer version of the traditional US 10A 115V 2-pin outlets. You could fit six (two rows-of-three) into the footprint of a traditional single-outlet box.
But high-density and wall-warts don't play together.
Must admit, the one thing I really find annoying about BS546/1363 outlets is the way the flex always exits at 90-degrees to the axis of the pins. It makes mounting them low-down on skirting-level trunking essentially impossible. Putting the flex exiting in-line with the pins (like the standard US style and Schuko -
https://upload.wikimedia.org/wikiped...px-CEE_7-7.jpg ) - seems oh-so-obvious so why wasn't it done??