Mr Punter

With the integrated fittings, if they are discontinued or you alter the kitchen you may not be able to get the right lengths. Make sure they are able to switch from the same place as the rest of the lighting.

I have seen these where they are bolted together on site. One of the lintels has some tube / chs welded and the 2 are bolted together. Needs SE design. If the cavity is 150mm or less you can use the HiTherm lintels. Expensive and long lead time on some, but good psi / thermal bridging characteristics.

Skirtings, architrave, flooring, plumbing, wiring, heating, ventilation. It is a huge house and a massive amount of work. Make sure you have not missed anything and you are not wishful thinking. How long do you think it will take you?

I doubt you will find longer than 6.0m. Can you break the span with a steel or flitch beam?

I suggest you tie a cord around the bung and secure it to a stake so it doesn't disappear down the drain under pressure when your side is full of water. I speak from bitter experience.

What is the paint?

The breather membrane is a good call. If you attach it with stainless staples it will give very good protection.

If you implement the planning you will be liable for the S106 payment. Once you get the paperwork your solicitor should be able to advise. That is a fair chunk for a replacement dwelling and you may be able to reduce this.

You could just use some self level compound over the adhesive to create a smooth surface. The LVT installers would do this in any case.

Yes that is a standard condition ("construct according to the submitted plans") and it allows you to apply for changes just with a variation of condition, without them needing to amend or replace the existing consent.

It looks like a bitch of a job. Have you considered just taking up the tiles and fitting LVT flooring? It will feel far less cold underfoot and they do a great range. With the lack of underfloor insulation - which should be 150mm thick minimum for UFH - you won't get a perfect solution. You may be able to incorporate some radiators for the problem areas.

We have had timber frame fire spread engineering a while ago. Stuart Milne - no longer trading - did the frame and Fire-Q did the fire stuff. It cost about £1000 10 years ago, for a 4 storey terraced housing project about 1200m2. The fire spread risk is mainly during construction. Once it is plasterboarded and finished externally it is far safer. You can mitigate open plan layouts with sprinklers.6293 Fire-Q FSRA Falcon Wharf Rev 02 FINAL 20062016.pdf

I vaguely remember that Building regs do not specify minimum stair widths.

That is a very well designed and executed car port which looks like it will stand the test of time, as well as the Scottish climate. Nice job.

Screwfix have a Trade pack of Torx screws on offer at 60% discount. 1400 screws for £19.49. https://www.screwfix.com/p/turbo-tx-tx-double-countersunk-multi-purpose-screw-trade-pack-1400-pieces/771vv I think @ToughButterCup is a fan of Torx.