Thanks for taking the time to do such a thorough writeup on this - it's fascinating to compare with the install we did a couple of months ago on our house in the UK.

We already installed a Daikin Altherma 3 air-to-water heat pump three years ago, which heats around a thousand meters of underfloor pipework + domestic hot water cylinder, but recently added a Daikin air-to-air heat pump. This is relatively new to the UK, at least in homes, so there aren't many contractors in the market yet.

Making good afterwards is certainly the challenge - I'm still repairing the plasterboard (drywall) holes, which I needed to make for access into the eaves. (I preferred this to having lots of external plastic trunking.)

I'm looking forward to seeing how the air-to-air heat pump helps with our winter humidity.