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I'd say not. If you'd paid someone, then there would have been employment taxes/NI that would have been paid on that wage, which HMRC hasn't received. You should take advice though, since you will have now developed for profit, HMRC may feel the gain should be treated as income rather than a Capital gain.

There are no visible joints on the frames. The only laminate joint visible is on the inner return of a sash: Below is on two different windows. The left hand image is the worst I could find. All others are more similar to the right image where the grain better disguises the joint.

Our Internorm windows have no joints on the visible surfaces, but finger joints are visible on the shut-faces, so can be seen if the windows are open. Our Solarlux SL90 Bi-fold is the same, although slightly better finished, so unnoticeable. I did like the Norrsken windows, especially the hardwood option which at the time wasn't that much more than Internorm's softwood option.

Personally I'd go larger, and with a similar set up, did. Family of five also, but with guests or a future owner it could be more. I went with 500l UVC, and can have all occupants showering within a 1 hour period, without running out of water, but the temp at the top will drop to 40°C from 50°C. I've not timed it, but recovery to 50°C is within the hour I allow DHW to have priority, from a 12kW ASHP. I was happy to go larger as I planned to divert PV to the tank, which I really must get around to... But, the 12kW ASHP can't modulate down to my space heating energy requirements, on all but the coldest day, so I have a 4 port buffer. Should I replace the HP in the future I'd likely downsize to 8kW.

I had the same issue visualising this. I've settled on it being speed/rate of transmission. Moisture moves through very slowly, air could as well if the pressure differential was constantly +ve or -ve, but that slow movement of air is effectively airtight. I have an Egger DHF tongue and groove outer layer that is both my airtight layer (no membrane) and vapour open...

As long as only the U Value differs. A UW value of 1,0 W/m²K is getting towards high performing windows where the Ψ value of the connection into the building becomes enough of a portion of the heat losses that it shouldn't be ignored. Then there's glass coatings that effect solar gain and air tightness. I found PHPP really helpful in this respect, all the windows I was considering were available as pre-sets within the spread sheet, so easy to compare one with another. Of course, if you're not calculating losses for a high performing new build then PHPP is over the top, so your ball-park calculations are as good as any.

Legionella cycle will be handled by the immersion heater in the DHW. The "Electric (Fast) Heating" will be an internal electrical resistance heater within the Heat Pump. The Legionella cycle should be unaffected by disabling the "Electric (Fast) Heating".

Yep. Switch it off, and only turn back on if you're struggling to get the house up to temp and you've tried everything else.

I've no experience of confusing guests with my own set up. The switches are seldom manually used for lighting, other than to occasionally change the scene from the automated one, but the switches do provide the ambient temp and humidity data to inform automation, as well as manually adjusting blinds, roof vents, manually boosting MVHR, setting the house alarm, setting house to night mode. They could also adjust audio volume, track forward/back etc. but I don't configure for this option. A huge benefit is being able to reconfigure any of the functions on to any switch positions.

Very few decisions in life only consider cost.

As you mention it's about whole house control. So, for me, it's to co-ordinate Heating, Cooling or just recirc (for moving energy from solar gain areas to North East rooms) across ASHP, UFH, MVHR (incl. wet duct heater/cooler), external blinds and roof vents. Loxone also controls the hot water return circuit based on presence sensing. Triple tapping is just an option on the Touch switches, if you want to emulate C4/Lutron then have a dedicated retractive switch, or bank of switches and have them etched/printed with the functions you want, but this wouldn't be my choice, it's better to automate where possible so that physical inputs are not required.

Only if you have it agreed that they owe you the DWG files. Do you have PDFs of the plans? Depending how they were printed/exported they can be of similar use as DWGs. But, DWGs are only half useful. They're a neutral file format for exporting between differing systems and loose any "intelligence" inherent in the authoring system. OK to trace around though, as are PDFs.

Your description sounds like you have a thermal store, not a UVC, but your quote in the OP is stating a UVC, so fingers crossed that's what is installed and you are misunderstanding how your UFH is working. A thermal store is not appropriate for a ASHP installation. If you only have a single tank, and that is a UVC, then when "on", your UFH is fed directly from your ASHP and the UVC is not playing any part of your space heating. There maybe a minor issue that Loxone can shut down your UFH zones (as they come up to temp) and leave insufficient volume of water open to the ASHP while there is still a call for heat and cause the ASHP to short cycle, but that's not causing you to use excessive electricity. Your ASHP has been correctly sized and the 300l UVC @ 50°C is sufficient for 3 people occupancy. With the size of house though, could it have a higher occupancy (with a future owner) and maybe a 500l tank would have been more appropriate? 32kWh / day for heating and hot water does seem a bit excessive, if that's the average from November to now. If however that was just for a few days when it was averaging around 0°C, then it's in the right ball-park. If it's an average then maybe you have an electrical resistance heater in your ASHP and your settings are causing that to come on to support the compressor and it's driving down your overall COP. Do you know if the ASHP has an electrical resistance heater? If so, can you disable it? The HP is more than capable of covering your hot water and space heating requirements without it, given enough time. When you say your space heating is set to be on "7 till 10:30", I assume that is 7am to 10.30 pm? Your house is similar size and performance to my own (and also controlled by Loxone) and I'd expect it to loose around 1°C per day with no heating on, so your 21.5°C for 15.5 hours and 19.5°C for the rest is effectively switching it off from 10.30pm to 7am, as it's unlikely to be dropping to 19.5°C. That should be fine on all but the coldest day as there should be enough headroom on the ASHP to put sufficient energy into the house in a 15 hour period (minus the couple of hours it maybe doing hot water). In short, there's nothing particularly wrong with your set up (accept it could on occasion cause short-cycling), so if you are using excessive electricity I'd look to disabling the internal resistance heater on the ASHP, if you have one.

You only need to put a Service void where you are running plumbing, and in those cases there's often another option, ie within cabinets, or false walls hiding a concealed system, or within bath enclosures, or...etc. etc. Suitably rated electrics can run within the insulated wall/roof. So you could be at 465mm for a very high performing wall/roof structure. You could go 50mm less on the I-Joist / insulation and still meet PassivHaus targets.

I'm not clear on what you feel is the advantage of building your own cassettes. I'm not sure there are awkward connections, there's just different detailing required compared to using solid timbers, and yes, if you need to fit to the side of an I-Beam you're likely to need to pack the web out to the same thickness as the flanges. There's a significant performance advantage to an I-Beam (or twin-stud) structure, it's worth investigating further. If you've also got a frame designer lined up that's confident, it takes the burden off you needing to know every detail beforehand. I've got a pretty comprehensive 3D model of my frame and am happy to post images of any junctions you are not clear on. Ply lining the window apertures gives a clean surface for the windows to fix into and an easy surface to tape to for good air tightness. The I-Beams weren't packed out though, the ply "just" went across the flanges.

Edit: Old story, I should have checked the publication date.

It is an Approved method, although you need to confirm it's OK for Aluminium. I thought Stainless and Aluminium touching was to be avoided due to galvanic corrosion. Mine is clinched on to hidden clipping brackets.

Is that to hold the capping on? Is it an approved (by manufacturer) fixing method? What metal is the roof. I'd not be happy with visible fixings, or holes drilled through the coated panel, or rusting hardware.

Looks very similar to BFP 21 L 3 071N0156 https://www.ebay.co.uk/itm/325254847243?hash=item4bbab31b0b:g:DyIAAOSwBjti0B65

Typo noticed after the 30 mins. "You should not need to press hard," Doh!

That's eliminated just about anything that could have been causing an issue. I'd just double-check the factory reset, as it sounds like this didn't work properly. You should need to press hard, but you should feel a micro-switch depress as you press down, and just hold in until the LEDs react. If nothing has happened after 30 seconds, then maybe it's bricked. If the factory reset fails, the it's try with the Bluetooth connection to your phone. Were your initial attempts via Bluetooth, or had you connected via Wi-Fi between your phone an the UDR?

But a bit like EVs from the 1900's they were pushed out by cheaper, higher performing fossil fuel based products. I believe for now, PU based foam thermal insulation products are fossil fuel based, but the industry is having to re-look at alternatives.

Is this not at research stage (for use as a thermal insulation product), with work still to do? Is there a commercial product available. I remember reading about blends of veg oil in fossil fuel based PU foams, but then more of the blended product being needed due to the reduced performance of the veg oil.

No problems with blown Cellulose here, ~0.1 ACH with no membranes. Can't say I didn't use tapes though, as all windows were taped and all penetration in the external air tight layer (T&G Egger DHF board) were either gasketed or taped. I went with blown cellulose primarily for its air tightness and acoustic qualities. At the time I was making the decision there were also numerous comments going around about PUR/PIR type insulations off-gassing and I wasn't able to quantify any potential risk involved with that, so went with the cellulose and other natural materials as much as possible.

It will if you have another Wi-Fi router running that your laptop knows the credentials for, as it will attach to that one and get its network setting from there, including default gateway. When you then plug the ethernet cable in it's going to see a second DHCP and router on 192.168.1.1 and grind to a halt. Probably best to switch off any other router and/or access point (if you have them) while you are trying to configure the UDR. They're very similar and I believe set up in the same way, with the same defaults.