Mike

This one is closest. However you need more in the bathroom - it's going to look too empty. A 4.5m wall in a en-suite is long and I'd be wanting to put in a double basin to use up some more of it. You may also have a problem with it being too echoey. Think about how you're going to finish the walls (tiles everywhere would be a bad idea) and whether you can get in any tall storage units or soft furnishings to break up and absorb the sound. It would have helped to have curtains at the window, but obviously not with the bath there. Personally I'd seriously consider putting double basins (or a basin & WC) by the window - so you can add a curtain - and put the bath (and WC) on the long wall.

I've done the same and would also repeat it. Much more interesting than a horizontal ceiling.

From where you are now, and from what you've posted, I'd with @Dave Jones's suggestion, though it will mean getting the roofers back:

I'm in France, but it converts to about £12 /month for 300GB with unlimited national calls & texts.

This. Trickle vents are there for a purpose and, unless you still live in a very leaky house despite the new windows, you do need a means of background ventilation.

I've been using a 4G connection with a huge data allowance for a couple of years. TV streaming isn't top quality, but but it's normally good enough for everything else. I have an Asus router tethered to the phone (Asus routers are one of the few domestic brands that can do that), and connect devices to the router over Wifi. So I'd suggest getting a GiffGaff SIM-only deal and see how it goes. I'd also put a duct through the wall so that I could install a fixed line later, if required.

If you can afford high-end hardware from a premium manufacturer, maybe. Otherwise no. Due to the running gear they're not quiet (which is especially a problem in a bedroom) and they often don't close properly. If it's a pocket door there are additional issues of access for cleaning, maintenance and repair.

+1 - so much easier & cheaper to print.

In that case maybe you should take a look at a gyroscopic driver. Don't have one myself (yet), but I like the look of them. For example this Dewalt: https://youtube.com/watch?v=1s6wZqNZ_34

I love good soundproofing between rooms, so I'd go for the first. Unless there are other acceptable options - planting some timber of the 4 x 2 studs to give more space, putting the ducts in a boxing, etc.

I remember how they would fill up alarmingly when you flushed, then just before overflowing there would be a gurgling woosh and it would all disappear. Yes, they did!

Anyone else remember siphonic WCs? There was one at a friend's house when I was a kid. As I recall it used much less water, was very quiet and very effective.

I'm not a gas expert, but I've found an interesting toy on the internet that may give some insights - a Gas Pipe Calculator. If you type in 32 kWgross as the consumption, 18m length and 22mm copper pipe (guessing that may be what you have?), it calculates a pressure drop of 1.36mb (millibars). Add in 6 x 90° elbows and the pressure drop becomes 1.64, which isn't a dramatic worsening (the calculator indicates that that's equivalent to 21.6 m of straight pipe). Compared to somewhere just below 19 millibars that Cadent told you. Then, if you upgrade the pipe to 32mm PE in the calculator, the pressure drop becomes 0.37. In other words, you would gain 1.27bar (1.64-0.37), which may push you over the 20 millibar limit. But that's a lot of work for around an extra 15% pressure difference. However if you currently have a 15mm copper pipe, then upgrading to 22mm makes a big difference.

It's been used on that other program at least once, in Leominster: https://www.granddesigns.tv/leominster As for the 'the house that 100k built', I most remember OSB used as the internal wall and ceiling finish instead of plasterboard. Aesthetically that's in the 'not good' category for me, but at least it could easily be over-clad when budget allows.

Correct. I should have said correctly designed foundations don't influence that, at all.

The wall & render are liable to cracking due to expansion and contraction of the materials used. The foundations don't influence that, at all. If you have cracking due to foundation movement you have a whole different problem.

For that length it's normally advised. The downside if you don't is the risk of a random crack which, in a minimalist wall, would probably look worse than a neat vertical joint.

Unless you have an obviously undersized incoming gas pipe, or an ultra-long garden / driveway, or a blockage, doesn't it seem unlikely that the size of the pipe in your garden is the problem? Wouldn't it be more likely that the size of the gas main, or the pressure within it, is the problem?

In general, I agree. If it was a driveway on very poor soil I'd consider geotextile but, in a domestic situation, not otherwise. And weeds will be seeded from above, unless you have an invasion of Japanese Knot Weed or similar.

FWIW, I'd choose wet plaster too.

A quick blast from a hose pipe with a jet nozzle will easily remove fresh snots a long way down the cavity. But not on fresh work (which the brickies should be cleaning anyway) and using a regular hose pipe, not a pressure washer.

Sure. But I worked in the industry and studied the subject, so it's easy for me. Without that background, there's a lot to learn and it will take a good deal of time. As @saveasteading says, £700 is a good deal, provided it's from someone suitably experienced.

Not for the Radon. Only if you have other good reasons to do so - for example as part of a package of comprehensive insulation measures or to install underfloor central heating. But even then replacing the floor is one of the last things to consider.

It's certainly worth trying, but their complaints process doesn't always work, unfortunately.

That's a good source of information. They also have some information about the most common solution - a retrofitted sump - here: https://www.ukradon.org/information/reducelevels_sump