When I was growing up, the living room was the main room we used (it also housed the dining table), and the other room was the front room which was hardly ever used. Then the council decided to modernise the houses and the two rooms were knocked into one room and double doors replaced the wall, so that the rooms could still be divided off if desired. It was at that point that the front room became the dining room in our house.
The kitchen was and remained separate to both rooms, and was never big enough to accommodate a dining table, so it was never a kitchen diner.
I think that many who bought their council house will have changed the configuration to make this possible.