I disagree an outdoor pool in the U.K. is great! I use the one at my mum’s house - like pp they close it in Oct and open it up around Easter.
It’s heated - they have the pool man out twice - once to open it and once to half drain/close it. Last year there was a leak so had to pay for various holes to be dug to try and find it to repair.
The running costs really aren’t that much according to my stepdad - just costs of heating and running the pump - my mum reckons it’s about £100/month.
They don’t need vacuuming daily!! A good netting usually suffice with a vacuum only when needed (although we cover it whenever it’s not in use so not much chance for debris) - usually every week or so. Similarly, it’s pretty easy to keep on top of chlorine- if it’s going green, it needs chlorine. We just put a couple glugs in and leave it uncovered for an hour or so. It’s as difficult as you want it to I guess.. (once you know the basics - and they are basic tbh)
I’m the one that uses it the most - it’s lush swimming in the rain and in the evening, floating around on warm days or “stimulating” 😂 exercise when it gets a bit cooler. It’s nice to sunbathe around and during the summer I often work from the pool (I worked remotely pre-covid).
When the pool is open I use it several times/week and get really toned and buff by Aug, then over winter I slowly become a pasty blob until the cycle starts again 😃
Agree with a good fitting cover - the ones that also keep heat in the water. Last year there was no pool cover for a few months and there were several animals in there over the summer (which doesn’t usually happen except the occasional frog/newt) 
I’ve heard it devalues a house (it came with the house), I guess it depends whether the house can comfortably carry it ie enough land etc. I personally see a pool as a definite “must have” in my ideal forever home, as if you enjoy swimming then you will use it, it’s so much better than a sweaty, stuffy, very chlorinated public pool and during lockdown it was an absolute godsend... I’m counting down until it reopens!