Mr Punter

Fitting it glued down is nice to have but a lot more time consuming to fit v. floating, as well as more expensive in materials. Should be good with UFH though.

Robin Clevett has a video on Lindab gutter install. Set the brackets so they do not clash with joints or outlets. Get the lengths up with a small gap between them so they don't foul on each other when fitting. Make sure you are happy before clipping into the brackets. It doesn't slide like plastic stuff.

I would rather see the cost of electricity reduced by scrapping green levies, high standing charges and reduce the link to wholesale gas price.

Agree just leave them although with hindsight the bottle gullies with the plugs would have been easier to rod.

I would consider using 22mm Egger Protect boards, glued and screwed. They are much more resilient and a bit stiffer. You could also use a decoupling mat under the tiles but it will add a few mm to the build-up and a bit to the cost. Flexible adhesive in any case.

I guess they are not on mains water.

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.