As a point of note, domestic air conditioning is close to universal in Japan ... but in the UK, less than 3% of dwellings have a/c. Even in parts of southern Europe that get pretty hot, such as Italy and Greece, domestic a/c is relatively uncommon (with penetration in the 20-40% level despite regular 32-42 celsius temperatures on summer).

The nature of the housing stock is partly responsible, of course. The average British dwelling is 75 years old; retrofitting central aircon to a cramped dwelling with stone or brick walls that wasn't designed for it is a lot hairier than installing pipes for hot water radiator driven central heating.