In Amsterdam/The Netherlands it's basically non existent in any of the older buildings. In newer construction it's becoming more common.
We live in in a an office building that I would guess was built some time in the last 15-20 years that has since been turned into apartments and we have some kind of radiant floor cooling/heating. It's not super strong but it's a hell of a lot better than my girlfriend's old ~1800s building with south facing windows. That little apartment turned into an oven in the summer.
1 in 8 homes was the last data I saw but it feels every day like a rarity. Some trains, big market stores, and restaurants have it but not to a degree you could count on it.
I'm not in Europe, but I understand that it's fairly common in some southern areas, but overall much less common then the US. Air conditioning is apparently more common for offices and stores than for residences.
Rolling out more air conditioning in Europe may not be a terrible thing from the standpoint of electricity providers. As things stand, unlike the US, where peak electricity demand is in the summer (due to air conditioning), Europe's peak electricity demand is in winter, due to electricity-driven heating. Having more-even seasonal demand probably makes life easier for the grid.
All that being said, I believe that the article is talking about unseasonably warm temperatures for October -- which is not that hot -- not so much extremely hot summer temperatures. This may not be a "roll out air conditioning" sort of thing.
30 planned today in the north of France, it was already 25 at 12h, I dare you to say it's not that hot, especially for freaking October. Those aren't so bad in rural areas but in cities it tends to be quickly suffocating.
Heat wave isn't +30°C. This is what climate change deniers want people to think.
A heat wave is when the temperature are higher on a certain amount of time. According to the IPCC, it's "a period of abnormally hot weather, often defined with reference to a relative temperature threshold, lasting from two days to months", and according to the Heat Wave Duration, and to the World Meteorological Organization, it's "five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5 °C (9 °F) or more".
I didn't do a ton of research but that seems pretty warm for October. I'd expect the average to be way lower (12° for the red dots maybe) with an occasional warm day or two.