Another idea for a no-Scotland UK flag. Like one of my earlier ones, this has similarities to the South African flag because of the sideways “Y” shape (a “pall fesswise” in heraldry). There’s no attempt to represent individual countries : instead, the three arms of the pall represent the three remaining UK nations. Red and white are the two colours common to all three constituent national flags, and blue represents the sea in which this island nation sits. Because of the colours, this still has a British feel to it.
Here it is along with the royal standard and various ensigns. The ensigns are proportioned 1:2 whereas the land flags are 3:5, as is usual practice in the UK nowadays
The background could be green, represent the land and green fields, and giving all the main colours of the three flags, but I prefer the blue: