JohnMo

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.

You use, the Daily heat loss power for min OAT the coldest day. In thee example below for Jan. So that gives you the total heat loss for your house. No. Total heat loss is total heat loss, if this is supplied by 100 or 1 heater it's still the same.

Sounds like the ventilation rates are not that good. If correctly set the air in the bedrooms should always feel fresh. We do get hot in our bedroom, so we just open the window as we feel. Our heating or ventilation doesn't get touched on a day to day basis. In fact ventilation doesn't ever get touched.

What's so special about them except the huge price?

£360 per panel

Exactly, the Passivhaus article above makes that direct reference. Our I stipulated the height, the installer did what they always do, set it 200mm higher than I stipulated. Didn't pay the final invoice until sorted at their expense - which they did.

I was thinking more like £5 over 10 - 20 years, that whole area needs to be insulated anyway, so no real thermal bridge exists anyway.

So your insulation is on top of the rafters? That whole area will need to packed with insulation anyway, so still confused where any size of thermal bridge exists.

Are using solid metal pipe? If so you will need cross talk attenuators

Not sure it can, there is a swinging flap that closes one port - the other port open, as the flap is driven to close a port the other port opens, most the transition two ports are open. Done two interlinked 2 ports would stop flow. Nothing wrong with a 3 port valve, they use the same actuator as as 2 port, so all the midpoint reliability issues are not present.

Do my jacket pots the same way, in microwave for 2 pots for 10 mins, in air fryer for 20 to 30min.

I am confused what thermal bridge you are trying to fix. Are they really? How is your roof insulated?

Funny you say that the was a comparison done in a football ground, where they installed an industrial sized air fryer. The air fryer chips didn't go down any worse than the traditional oil fried chips in a blind test with the football fans. As I said took a long time to be converted but if you like crispy chips they are great.

I really wouldn't worry the restriction is for a very short length. I heat my cylinder via 22mm primary to a 28mm Honeywell diverter with no issues from a 6kW ASHP. Your cylinder may come with a diverter - mine did, so worth a check

Make sure the diameter isn't an access issue, if you are going through a loft hatch

Get an air fryer - way better chips. Took me awhile to be converted

Prices were on there way down prior to COVID, then prices shot up with the shortfall in production, prices are now reducing again. Trouble with PV the models of the panels keep changing, the prices fluctuate a lot. End of line stock will always be cheaper, same as slightly lower performance panels. Wait you maybe ok, wait you may not, who knows.

I did and it's included in another recent thread. As @Nickfromwales says payback is a life time or two. With a heat pump something like 50 to 140 years depending on the tariff and how much you actually loose from a standard cylinder when water is stored at below 50 degs and how much you pay for a cylinder. I did add into this the loss of CoP as the full recharge has to be completed at full temperature instead a slow ramp to full temp for a new cylinder. Bonkers idea