JohnMo

I would do that extra step, make system balance out the box. 1st image just delete the red loop use the blue and green loops to heat those areas as well. Each loop is only 60-70m long so you have plenty of scope for this. Then in bedroom do whichever is easiest to install. You certainly do not need much heat in a utility room.

Architect did the topo as part of the initial planning. Cost me nothing for the GPS mark out, the ground workers included in the costs they quoted me, GPS is part of the base scope.

My guy (arranged by our ground workers) came with drawings loaded into his computer, tied into GPS, then using another bit, just picked the points of one by one, even told me exactly how much higher the site was to the plan. Marked out the foundations, once foundations were done, came and marked out for the blocks. Spent an hour or so at site in total. Technology working. Check measured it all and couldn't find an issue and foundations are pretty complex, compared to anything else I've seen.

Maybe even the person that empties your bins. Obviously had zero idea how to manage drawing revisions.

That maybe the issue (haha) - technician, not an engineer.

You may need to edit replay 350mm or 150mm?

Run it like a proper contract. Weekly progress meeting and minutes taken with actions and agreements stated in black and white. You discuss work scopes and money. If the workers are not there half the time, ask yourself and the builder why aren't they. You should only have about 10 to 16 weeks work to do, from the scope you described depending on house size.

You just need to keep simple, otherwise you will procrastinate and never get any generation up and running.

Why not use mineral wool then zero cutting?

Check the diagonal dimensions to make sure it's square, you have nice oblong building so should be easy to get right, but ...

Trouble is the ideal angle really changes on a daily basis, even an hourly basis if you wanted to be really fussy. I just have around half my panels at 45 degs and the others vertical. Also have 2 set horizontal and they generate nothing mid winter. Complication added, really depends on export limits if it worth changing angles (and if you actually get paid). We are limited to G98 exports, so even in February we get plenty of clipping in the middle of the day if the battery is already fully charged. So no benefits for me, having the complexity. Simple fit and forget

Only if your flow temperature is stupid high. Long outdoor pipes benefit from lower flow temperature, aim for a max of 35 and you will be fine. Then you will be fine with 25mm insulation.

My heat pump is behind a shed and pipes go underground to the house. No real need to go next to house. But the units mentioned by @DamonHD and similar units would be a super easy swop, no plumbing to do. Concentrate on downstairs rooms and maybe panel heaters in bedrooms or leave the storage heaters in those rooms.

So we are talking £600 in panels, plus mounts. Couple of hundred for an inverter? Solar is still pretty cheap at the moment, getting more expensive by the day. Buy don't faff

What outdoor space do you have, garden etc? Flat roof?

Good luck - can I ask why?

Or just do an ICF, stack the blocks fill with concrete, U value 0.14 with service void. Parge coat for airtight if woodcrete, no need with polystyrene blocks. Our house, 4 weeks (end Nov to Christmas, bloody freezing) 70m perimeter and average 3m tall, two of us never done it before. 2 days to parge coat internal wall.

Think that 33% more complex than you need. Stud plus internal OR external, NOT both

Do you need the internal breather membrane? Cannot see what that does. Between studs knauf Frametherm 32, easier to install and better U value. I would do a simple twin stud, fill with frametherm 32, or blown in insulation. OSB board outside with membrane. Or 140mm structural, OSB outside with membrane, internally PIR skin over studs to achieve u value

Are you seeing any issues yourself?

Don't overtighten fitting with olives.

That really doesn't mean it complies. If you structural engineer says nails, that's what your structural design certificate covers. If you want hooks, make sure the structural engineer is happy. Pretty much don't comply with any of that. Full fill Icynene, open cell foam. Proctor Roofshield, so a very open membrane. Full double taped vapour control membrane and service cavity inside house. GSE trays have plenty of air channels to allow ventilation. When generating plenty of thermosyphon driven ventilation also.

We did integrated solar and slates. The solar trays are screwed directly to sarking. The slates are copper nails direct to sarking. Breather membrane on sarking boards. Slate hooks, do they comply with the Scottish wind loads?

The sarking boards do that, with the breather membrane. When they fully dry there is a gap between each board. Not sure why the architect has shown battens on the sarking, with real slate they are not needed.

I would push back on 170mm kingspan between rafters and use a more flexible and very easy to correct mineral wool, something like Rockwool Flexi. Do it thicker to to U values. Same for walls, but you may need to increase the 25mm inside to something a little thicker. Back to your question, it looks fine, well protected. On your 1st floor joists you may need to be wrapped to join the 1st and 2nd floor wall VCL to join.