JohnMo

Think it came in manhandled sections and was pinned to the ground with bent rebar pins.

Big scale

I did a small area on a 50 deg slope, a couple of years later the bags have all rotted away, but it does give time for the plant roots to take over. Much less labour intensive is the correct landscaping mesh then back fill with soil.

Use Compacfoam CF200, 75mm x 100mm. From Green Building Store. Took the joiner 30 mins to do 2x roof light up stands. Might look expensive, but not paying a joiner to faff about for 1/2 a day. Super simple, zero cold bridges. I also lined the whole space with 25mm PIR for belts and braces.

Sounds super expensive - any other practical route to get to basement, do you need the sand craned in?

Why not? Get rid of the worst condensation where it occurs. Have 2 directly above showers, the other directly above bath.

What does that mean in reality? Have you looked at cascade MVHR, such as blu Martin or Fresh-R? Or a home brew version?

Not sure then either, as long as it's filter and UV treated, and you use most of the cylinder contents daily again no need.

Our 1830s house (last house) had the rubble, stones and general building waste all shoved in there, almost no noise transfer. Lathe and plaster ceiling and thick pitch pine floors.

You actually run that? Why?

I have just been away since Thursday visiting. Was like a breath of fresh coming home, light, fresh airy feel, as soon as you walk in the door. Good old MVHR.

My Atag boiler did that also, unless you have UFH then it just screws the system up because the dalay caused by the floor heating up, same as Mitsubishi heat pumps do - they say not to use with UFH.

5 requires dMEV or MEV, this has been the case for quite a while also

We have 4 houses about 1/2 a mile away all use WBS and if not windy it stinks.

My sister replaced a pellet boiler last year for oil, saved a £1000 in energy cost in one year

Evaporator is on the wall side of the heat pump, so always in the shade, sun would never get close to the area to be effective with aiding defrost. Your heat pump reads the air temperature it sees going via the evaporator, compare it to ambient on a sunny day and report. Mine is exposed to early sun, if it's cold and sunny the air going through the evaporator is also cold.

You do need to start with this approach as the heat pump is really needed to be 3x oversized for the house (so maybe a typical MCS install). And have a smart meter that actually communicates (unlike mine). I run E7 with 6kW heat pump and 60T of floor. My heat demand is 3kW and on the coldest days I need to pump heat for 12hrs. So in my case the cost for the same amount of energy (electric 14p kWh) is £560 instead of £300.

Why would that happen with a well set up system. He has UFH not radiators. My gas system started with lots of zones, consumption of gas was through roof. Did various forms of WC (with a d without zones), fixed temp for long periods works really well. I did lots of experimenting with the gas boiler and batch charge worked out cheaper with that also.

As above, also the unit is pulling a huge volume of air through it, so it's making its own strong wind. (Bold section) No

That makes no difference, except make sure it's a heat pump suitable for a coastal location.

I bought my two units as new (other) units on eBay, one came with a faulty fan motor. Titon were great, although out of warranty, they helped identify the issue supplied parts etc, at my cost. Now been running for a couple of years no issues. Like that you can speak technical to someone in the UK, get the parts quickly and easily.

No idea on cost comparison, but stud walls are quick easy, double bottom rail single top rail, and the verticals at 600mm centres and noggins at 1200mm centres. All wiring in drilled holes in studs (3x2 non structural), 50mm insulation, plasterboard, done.

You shouldn't need to take it off for the life of the building. Having seen it applied on our doors of the last house, I would avoid if possible as the surface finish is pants

So your area never freezes, you have a min temp of 0.6. You should really follow what @ProDave says or use these instructions as a sizing guide

Our last house was originally built in 1830, some insulation improving done but not much. It was a heat sieve, we never had bedrooms heated, our bedroom window was open 360 days a year, a few very cold nights closed.