In our London apartment leasehold, we have a water-sourced air conditioning unit. No external condenser required, it instead dumps the heat into the waste water. It has been incredibly helpful during this heat wave as someone who really struggles in the heat and works from home.
It's not ideal during a drought though to be using water like that, it would be nice if we had a grey water tank system so we didn't have to waste drinking water. It doesn't seem possible to install a grey water tank like that in our apartment though. Given our apartment already has district heating, there's not a super strong reason why it couldn't have district cooling as well, but the regulations are not in our favour here.
We installed it all without planning permission, although it still might require permission from the freeholder depending on the rules regarding Service Media alterations (as it requires new plumbing for our mains water).