Wales though, isn't going to be at the heart of the heat wave. Them having oceanic climate and being pretty far north already, they won't be as hot. But I was surprised to see, that even there it's going to be more than 30°C for a bit.
Other countries like Spain, France and Italy are gonna experience the real extremes, with temperatures as high as 42°C in some places. Fortunately, AC is a bit more common there, as they are experience higher temperatures more frequently, but still.
In Germany, where I live, we're not very well prepared for the prolonged heat, and AC is still pretty rare here, especially in homes (and somehow has a bad rep).
We have a culturally ingrained technique to deal with it, by blocking out direct sunlight with our window blinds (if you haven't seen our common blinds, watch this: (https://www.youtube.com/watch?v=_KePLmie7lE) and airing out the house at night to cool down the building. This worked pretty well for the climate that used to be. But for heat waves like the one in front of us, where it doesn't cool down below 25°C we'll reach our limits.
I'm so happy to live in an appartement, that recently had split heat-pumps installed to replace it's old school electric heating system. Those can be used for cooling as well.