DamonHD

I deny everything.

This ought to be a poCcast, to rival Joe Rogan...

Well, get one that is water- and energy- efficient, that she likes, I suggest. Cold only is fine.

Both circulating hot and washing unnecessarily at 40C or above are huge consumers of energy. (And washing too hot ages clothes prematurely.) That costs money and climate emissions. The OP was talking about 'savings' from a dual-fill machine. Better savings would come from NOT having circulating hot and NOT washing hotter than actually needed.

One huge energy saving (~80%) is to run washes as you can cold, so buy a machine that can do that. We do everything except bedding on cold. https://www.earth.org.uk/note-on-Zanussi-ZWF01483W-freestanding-washing-machine-REVIEW.html Also as @JohnMo says, a water- (and thus energy-) efficient machine may not draw enough hot for it to reach the machine at all from the tank/boiler.

Season 2 will involve glazing of some sort, surely?

No one here but us chickens (and Steamy).

May be relevant: https://midsummerwholesale.co.uk/buy/solshare

Moving?

Well yes, I had Octopus redo the calcs with some extra information and the heat loss was halved and only one rad needed swapping. Octopus has to tick some MCS audit boxes, but are open to rational haggling in effect. After some observation including a couple of days that hit design days (-2C outside) I adjusted my weather comp to (50°C/-7°C, 25°C/14°C). https://www.earth.org.uk/heat-pump-16WW-control.html#weather

I adjusted the weather comp curve immediately, so we don't get up to 50.

Yes, just did for me in November: https://www.earth.org.uk/heat-pump-16WW-control.html

We we meant to have stopped nipping round in the night to pee on your walls yet? The train fares are getting too much... Also, I'd like to check that I have the right address...

For at least one of my 3G units the nominally-expert third-party fitters left a ~1cm gap down one side of the unit, which I only discovered sometime much later, so basic errors can happen...