JohnMo

That's because everyone is brain washed by plumbers wanting to install 30kW+ boilers. Doesn't that far out. MCS start doing 2 or 3 ach which soon racks up the heat loss. Your calculations assumes the room above is also heated, which is fine if it is. And should be with ASHP anyway.

Effectively completely ignore the GSE instructions, they are not applicable to a sarking board roof. Attach the trays direct to the sarking, through the membrane

You have self balanced actuators, maybe it was just going through a learning period, some can take quite awhile. With SQ610, you have a setting that optimises control to the Salus self balancing valves. Go on to Google and search for the full instructions for the SQ610, not the quick guide that comes with the thermostat.

Buy the correct aluminium capping pre made. You will not get a sharp bend without a proper bender, and depending on grade of aluminium it may crack.

So do you have an issue?

Not sure I would ever hand that over to someone - what you actually want and they will assume is ok for will be very different. Do your own leg work. Get the right architect they will handle that for you. Turnkey and to first fix are very different. Turnkey you give them an empty site, you then move your furniture in. First fix is generally before any plasterboard has been installed. Lots of work to do after 1st fix

Long reply Sorry it's huge. You need good modulation at the 7 degrees point. But it only modulates down to 4.32kW at 7 degs. Our winter average temp is around 7 degs so your heat pump spends most it's time in that range of output. Your heat demand at design point is lower than that. But their next size down, in real terms, is too small for your demand. So you will get cycling and have a hard time setting it up. Your scop is likely to be high 3s. But if you get a more appropriate sized heat pump your SCoP should be low 5s to mid 5s. My current heat pump is 6kW, but since purchasing I have found it's actually a software limited 10kW, modulation is similar to the Cool Energy unit. I have got it running acceptably, but it's just took big a mild temps. So that has a few impacts - Your target flow temperature is higher to make up for cycling. It was 7 degs yesterday target flow temp was 29 degs, cycling was 40 mins on 90 mins off. So I got a cop associated with a 29 Deg flow temp, CoP yesterday was 4.6. However is it didn't cycle and ran steady state, flow temp target would only need to be 23 degs and CoP would be closer to 6.3. A saving of 2.3kWh as a good estimate on one day.

Guess I should have looked at the spec correctly - yes 25A, not 100A.

Two basic models, WQ610 is for radiators and SQ610 for UFH. If you have a WQ on UFH and you have any self learning functions active, the thermostat loses all control as the algorithm is wrong for the application. A WQ will work with UFH, but only if you use in a simple on off mode. Been there, done it, got the tee shirt.

I have a SONOFF POWR3, it will do a 100A, so driving an immersion is a walk in the park. Have in parallel to an immersion time switch. I used for PV diverting. Pretty quiet, will connect to home assistant if you want.

A GivEnergy AIO comes with a default setting of ECO, this can be switched on or off. Turning Eco Off requires you to set specific Timed Charge, Timed Discharge, or Timed Export schedules. So set eco off, you can set the charge during a cheap period and set a timer discharge this would discharge to house until flat or time window has elapsed. It would ignore PV so it would all be exported. Once battery is flat it would remain so, ignoring any PV until next charge window. You can also schedule a discharge to grid. This an AC coupled battery

Which quantum model? There is one for UFH and one for radiators. Do you have self learning stopping starting on or off?

I would check the thermostat settings and your controller. If rooms are 10 degs and you have the thermostat set at 8 degs, where is your boiler call for heat coming from. More details needed

Should that read UNWISE?

Trouble with a lot of MCS installers they simply ignore all improvement made to building fabric. They then apply a huge ventilation heat loss if you're not careful, then add a bit just in case. As said by @crispy_wafer do your own calculations make sense of everything in your own head. I recently asked about a heat pump quote via an umbrella scheme, they had my EPC, my house drawings, quoted a 12kW heat pump. I have just bought a 4kW, without grants.

The normal run of things You charge on cheap rate, battery depletion starts on expensive tariff. As PV generates it go to charge battery first, then when full, any excess not be used by house, goes to export. Any variation from this is robbing Peter to pay Paul.

Fan coils work well for cooling and heating, but as with radiators they need to be sized correctly for the heat loss first and then for the cooling load. So you need proper room by room heat loss calculation. You basically set the cooling flow temp to match output needed. That flow temp for cooling can be anywhere from 6 degs to 20. The fan coil fan speed modulates to match output needed in a micro scale. Running cooling below about 14 degs required condensate drains at the fan coils.

Jotun https://www.rawlinspaints.com/products/994-jotun-penguard-express-zp.html?gad_source=1&gad_campaignid=23257329793&gbraid=0AAAAADwqu94V43vCFb8yzShst-tZZva6u&gclid=Cj0KCQiA1JLLBhCDARIsAAVfy7h-TKMmfT5USzPcfuXTp4QE_N1p81iHyvb7ZFyBlLtiTim2umqRhRIaAsTlEALw_wcB The linked is a high since phosphate epoxy primer, can be applied with paint brush or roller, even though the instructions say to spray paint. Epoxy isn't that UV stable, so would need a top coat. Prep to give it nice rough surface to put on to, then it's there for life and stops rust well. I used on a 50+ year old Beetle floor pan, 12 years ago, still looks like the day it was painted (not been on salty roads though)

Hot dip galvanised? If installed maybe not. Best coating by far is Epoxy, not cheap, but great.

That isn't good enough for a heat pump, you need an accurate assessment. My house is 192m² all vaulted ceilings (225m² including plant room) my heat loss is 3.5kW at -9. Just about to remove a 6kW heat pump and install a 4kW one. Not the correct way to go about heat pumps. Not really correct for has boilers either.

That is one huge heat pump - are sure you will ever need that big? Oversized heat pumps are not good. Correct sizing is important. Integrated systems are almost never needed. Keep ventilation separate from heating. Don't waste your money, heating is only good for 10W per m² of floor area, cooling via MVHR is crap in the UK due to low flow rates and humidity. Just use a normal heat pump cylinder (more later) Yes, but choose based on actual heat demand at -3 (location depending) and more importantly min modulation at 7 to 12 degs. Work out heat loss at these temperatures and choose a heat pump that will modulate down to that level. Home automation - just isn't needed. So system layout PV and battery let them run on their own, supplying house and export excess. Keep it simple, no integrate quired it's there by default. Heating, fan coils is fine for heat and cool. But again keep it simple. Ventilation IF you are airtight better than 3 and are strongly making airtight decisions then ok. Just have it do ventilation nothing more nothing less, it runs in background 24-7. DHW, you can have ASHP do hot water, if so just choose a cylinder with a 3m² coil. Or heat during off peak periods via immersion, with solar real cost difference is that big. I have run every mode of heating control with a heat pump and weather compensation wins, on comfort, costs and ease of implementation. No third party control is needed and adds to running costs. It run priory hot water mode, it just switches from CH or cooling to DHW. No issues. No your just making it complex in your heat, each is a separate standalone solution that without the box without over engineering Battery and PV work out the box Ventilation set and forget (except filter changes) ASHP set WC curve, get on with your life DHW either set a stand alone immersion timer, or get the ASHP to it via a schedule.

ToU tariffs have existed since the 70s (E7 etc) so no idea why they will just disappear. Format may change, but that's life. Have managed the battery in simple E7 and now Cosy.

I would buy a long small dia drill, that can go through the whole lot, drill to give the fall you need in the duct. From there you have a centre for the duct. Mark up the diameter you need. Then drill a pilot hole and use a jigsaw to take out the hole, repeat on the other face.

All I know is from my own perspective, I almost never pay more than low rate Cosy even when its -5 outside. That's with a 13kWh battery and cosy tariff. (So 15p per kWh).

I think I would step back a little First decide what your running logic is for the immersions. Are they all switched together, one heating at a time etc Then test is that the right logic to take - is too simplistic or just way to complex to make sense for anyone else to try and fix it etc. will save you energy, will things fight each other etc Then when that is all making sense, plot the best control approach and from there how best to configure the wiring.