Mr Punter

I have had a contractor not use the Compriband and their stuff has turned to crumb in 3 years.

I have had big bifolds in the past and they were rarely opened. The best I had were 3m wide in panes, so you had an every day access door plus the open up all thing. The downside there was we did not have a window in the same room that could be opened gradually for ventilation, just a big fixed pane. Sliding doors allow adjustable ventilation and are what I have now. Regarding door height, 2.4m is probably high enough. Do not get them sized near the maximum extremes of what they are able to make, as this will often mean that the running gear / hardware is working at its limits.

Scaffold tower and get Mrs to wheel you along between cuts.

Could it be better to demolish and rebuild so you are not constrained by the existing structure? You would also get the VAT back and have a brand new house. I doubt there would be much difference in the costs.

Yes, for first floor you could bin the 50mm insulation, UFH and 75mm screed. 40mm flow screed would get you nice and level. Towel radiator are all many on here have for first floor heating.

A special prize is needed for Best Thread Title.

+1 OSB for racking, breather paper, battens, cement based siding / cladding boards.

Will they accept a professional consultants certificate? Some of these can be issued retrospectively.

NHBC like a drained and ventilated cavity in the construction. I can see why.

Screw a large piece of ply or osb behind the rad, into where the studs are. You can then screw your rad brackets on where they need to be.

I have looked at their other posts and they are having issues getting a fixing for the rads! https://forum.buildhub.org.uk/profile/3234-phloaw/content/

For sprinklers in the building our contractors used Blazemaster pipework. 85% of the cost is for design and first fix. You really want it tested before you plasterboard. It is good to get a separate water connection for the supply.

That was a warm pitched roof, in the meaning of insulation between and under rafters.

The water will get in through those hairline cracks. Perhaps a low modulus sealant like https://www.screwfix.com/p/no-nonsense-builders-silicone-grey-310ml/912gr

£9,384.00! At least there is free delivery. Is there much benefit in having the hybrid compared to a modern ASHP and oil boiler separately?

Not sure how the feature stone is supported? Do you need a single leaf l-shaped lintel in addition? Could use some galv or stainless angle for the outer leaf?

I think @Gone West has a decent idea. Demolish the lean-to and build another extension the same depth as the shared one with a valley to link the roof.

If the policy is to get people to switch from gas to electric, they should be increasing the cost of gas and perhaps lowering the price for electric.

Just a small fascia board. Choose any gutter you like the look of. You could have stainless or copper. We have black powder coated ali with small fascia.

I think you could put some Lindab aluzinc gutters on and lose the soffit overhang and it will be fine.

You could get the BCO signoff before the wardrobes go in.

Could the windows be supported off a steel beam with pad foundations?

Can't you put a small hatch to the right, under where you have had your pocket squirrel out (again)?

https://www.fhbrundle.co.uk/ and https://swr-balustrade.co.uk/ may help

Would a continuous dry verge help?