In 1945, the UK had far fewer people and it still had some slack when it came to resources such as land. Much of this slack has now been exhausted.
"The population rate of increase has been pretty constant since 1945" is actually a problem. This kind of eternal increase is not sustainable on a smallish island whose northern and western half isn't very suitable for housing.
It seems weird to single out population growth when bringing up unsustainability of growth. To address that an entirely different economic system will have to be created.
"The population rate of increase has been pretty constant since 1945" is actually a problem. This kind of eternal increase is not sustainable on a smallish island whose northern and western half isn't very suitable for housing.