We have just installed an Australian Energy Systems Heat pump. It’s not in use yet but I can report back once it is. I’ve attached a link to a company in Sydney that install them. I did a lot of research and nothing else comes close to the efficiency of this unit. It’s also full inverter. We went with the 45 model which is a size up from what we required. They make units to suit any pool. It wasn’t really much if any more expensive than an Astral etc for the kw. Our unit has a COP (unit of power returned for that used) of 16 in summer which is about 4 times the Astral equivalent.
Inverter Pool Heat Pumps, up to 50% More Efficient :NCS Pool Heating
Thanks for the link Riley, I'll have a look tonight. So much to read at the moment!