COSTWAY 12000BTU Mini Split Air Conditioner& Heater, 20 SEER2 115V Wall-Mounted Ductless AC Unit Cools Rooms up to 750 Sq. Ft, Energy Efficient Inverter AC with Heat Pump (Blast Series)

They are actually laughably cheap now. Hell, Costco had a window AC unit which would easily cool an entire European home for $279 the other day, literally the best window AC unit on the market too. And for a more permanent installation, you could get something like this: https://a.co/d/08AuoEZE Like $600 all done for an easily installed AC unit which would be plenty to keep a small European house cool.

You guys live in miniscule homes. Drill 1 single hole in your wall, install a $500 mini split that is insanely DIY friendly (even the British can figure it out) and then plug it into an outlet. Whatever the British version of this is: https://a.co/d/08AuoEZE And you can use it as an inexpensive heater in the winter.