Conor

You can temporarily wedge the toilet up on some wooden blocks and slip the lvt under. Assumes you have a Flexi supply pipe. You only need 40mm or so.

Get a couple opinions from roofers. If it is due a strip and reslate in the next decade or so, makes sense to do to it now. Use in-roof trays, keep all the slates, use the best for the roof and the rest as spares. And get a roofer to do all this, not a PV installer Old buildings have these big costs now and again.

I used adhesive underneath and 180mm concrete screws with washers.

Use an air admittance valve and ditch the SVP.

If your joiner has said 900x2090, is assume he's allowed 25mm or so wiggle room. 905mm will be fine, worst case you might need to chip at a bit of wood. I'm assuming this door will be a saving for you compared to a bespoke order?

Make life simpler and better, have it all the one level. Drop one by 200mm, raise other side by 200mm. Keep ridge heights the same. Would it make a big change to the appearance of the house from the road? (i.e. would anybody notice/care?)

I know?! Some people think they sound like a motorway at rush hour or flight EZY665 on takeoff.

Our cool energy 9kw isn't any louder than a large office fan. The only time it's noisier is when on cooling mode, when it sounds like an overboiling saucepan on a stove. But that's like 5 days a year.

Would you not just raise the ground level with stone and pave? Would be a lot simpler and cheaper.

Without commenting on the calculations and assumptions, a 5kW will struggle. If the max output of the heatpump is the same as the heat loss, when it's cold, the heatpump will have to work 24x7 to keep the house warm. So no time for heating water. And if the COP isn't at what the point needed to produce 5kW, then your house won't maintain temperature. I'd be looking at a 7-9kW heat pump.

100% agree with @Gus Potter When we settled for ICF, the first thing I did after learning the basics of ICF, was scope out contractors. There were basically four guys in the entire country that did icf at the time. One was discounted due to not so great reputation. Other was just too busy. So was down to two. System didn't matter, as Gus says it's just formwork to hold the business end of things together. Drawings based on generic ICF and requirement in the contract to meet the required U values, so was easy to send out and get prices. Building again, first thing I'd do is look at what is done locally, and take it from there. Personally, I wouldn't use ICF again, primarily because of the huge embedded carbon figures, I'd be going timber frame, cellulose insulation, with brick outer skin.

I'd move it. Those plastic boxes don't last long if driven over. They may even refuse to install.

Keep it simple, get and induction hob with integrated downdraft recirculating extractor. Lots on here (myself included) have that setup and are very happy. No ugly, cumbersome bulkhead over your cooking area either. Architects are not kitchen designers ...

Compact foam

usually, no. You need to dig out the wayleave agreement and see what the conditions are. you can usually plant shallow rooted plans etc, but not build anything hard.