Japan's trains have aircon but often it's not cold enough, and at the parts of the year when the climate moves from hot to cold or cold to hot you might find yourself on a train with heating still on because the calendar date is still "winter" even though it's a hot and sunny day, while you sweat profusely and feel irritated about the seemingly widespread inherent inflexibility of the Japanese.

Osaka's Hankyu trains are full of ads for musicals (it owns the Takarazuka Revue), I think that all this shows is that London has a far more vibrant cultural scene, which is apparent at all levels of society. I'd rather see ads for musicals than the ads for male hair removal clinics.

as for the uk train stations, the temperatures are in part due to their age - London Underground was built in 1870s, and since that time rocks accumulated so much heat that it is extremely difficult to maintain human-friendly temperatures. Japan subway is 70 years younger, so it’s easier for them to maintain temps.

(And my hometown Warsaw subway is even younger - 50 years, and we don’t have AC whilst temperatures are at a perfect level).

What London underground might need is not AC, but a process to cool down rocks - importing coolness during winters. To maintain equilibrum you’d need to pump out around 1TWh heat every year. To bring it down to normal levels in say 20-30 years you’d need to pump out 2-5TWh a year.

London surface trains have aircon, as do many underground lines.

I cycle most of the time to be fair but that doesn't tally at all with my recent experiences of peak Oxford Circus