In this area SE Canada summers are usually low 20s usually 25C is a typical hot summer day, but now 30C to 35C seems to be the new normal hot, I think it got to 38C this year. It's also very high in humidity here 80% to 90%, which makes sense being on an island.
Anyway dad has a lung disease (IPF) and heart problems plus bearing 70 years old and overweight, this portable unit I see almost as life support.
It would be bad for any elderly person to die due to the heat but I think in area where it only gets hot for a month or less it's deceptive. Most elderly would think it wasn't hot in the old days and they can't afford or pay for an AC unit and will probably die from heat stroke.
It is not possible to deal with (humid heat) without modern technology.
The only workable evolutionary way to do it would be to significantly shut down self-heat production, short of a biological heat pump (that does not exist AFAIK)
But of course, in the UK, it's hot for a couple of weeks, as opposed to the US where depending of the region is hot from half-year to almost the whole year.
Here in the states, my house had no AC, and we have weeks of >100°F/38°C summers with high humidity. All your fine mammal evolutionary adaptations are useless. Panting? Nope, air is hotter than you. Sweating? Nope, won't evaporate. Radiating from hairless skin? Nope. We did have a tiny window unit air conditioner that about half worked that came with the house. We'd build a tent over the bed and just barely stay comfortable.
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[1] But not many. I just looked in amazon uk, and your choices are slim compared to the states. I say free standing, because a window unit can tear up the window frame pretty badly and if you are renting that isn't polite. The free standing units just have an adjustable width panel with two holes that you shut in the window sash.