Cheddar, Red Leicester, Stilton, Gloucester, etc - all hard.
Camembert, Brie, etc - mainly soft.
How come?
Stilton is hard?
ETA: List of soft British cheeses (the French version doesn’t sort by hardness). Blue cheeses aren’t sorted by hardness.
I do know that hard cheeses are designed for long-term storage, and soft cheeses are meant to be eaten right away. Would differences in climate and ability to store fresh milk be a factor?
What made you choose these cheeses as representative of the entire country’s cheese output?
You’re going to have to define “mostly” for there to be any possibility of a meaningful answer.