I'm not quite ready to have tradies in my house for a proper fixed heat pump installation, but I wanted to get something a bit better (more efficient, less noisy) than my ancient single-hose air conditioner.

So today I've ordered one of these:
https://www.heatershop.co.uk/prem-air-eh1960-4-1-split-air-conditioner-with-app-control-12-000-btu

The SEER and SCOP look good, the quoted noise levels are reasonable and it's not quite as expensive as I expected (although half the price would have been nice).

Will share more info when it arrives.