The build

That's more friendly than I thought. I assumed you would need a plant room for all the kit. Oh, my mistake,  the plant room is the polytunnel

P says thank you and he's deeply envious. He's been researching  MVHR (just out of curiosity) it wouldn't be feasible for our old bungalow though. He'd like the opportunity to have a new build with all the tech, but neither of us would cope with the troubles, trials and stress you've gone through, let alone me having to make decisions.  It just wouldn't happen

I wonder how many new developer homes incorporate the tech available now. I think solar/grey water and rain water recovery should all be mandatory.

I doubt many new developments include things such as mvhr although I think air source heat pumps are fairly commonplace.
There's cheaper ways of building which is what developers will aim for as it will increase profits.
Strangely grey water harvesting isn't something we've ever considered, we have our own water supply (nearest mains water is over 10 miles away) and we get over 100 inches of rain a year, water simply isn't a scarcity for us