Mr Punter

I have used Resistant Board. Much cheaper than Superlux. It has a fibre mesh reinforcing as well. It has all the certs. They are pretty helpful as well. https://www.resistant.co.uk/

I was not sure if you were after a painted finish? Be careful as some of the door blanks are really heavy - make sure the sliding door kit is up to it - you may find lighter weight blanks available.

There are loads of places that can supply these. Just googled https://www.howdens.com/joinery/doors/howdens-solid-core-blank-plywood-flush-fire-door-obj-sku-family-25306489?productFamilyId=DXF0048&skuId=DXF0048 https://www.lawsons.co.uk/product/2440x1220x44mm-exterior-door-blank-fd30/j05500010 https://www.emerysltd.co.uk/fd30-hardwood-door-blank-c2x27285914

I think that metal studs are going to work much better. They do a 50mm I stud which is good for an independent wall. If you can add resilient bars the sound proofing would be even better and with these each side it would take another 30mm or so. The acoustic matting is good but heavy and expensive.

I would ask the council for an example completed one for a system based on domestic smoke detectors. This will establish what they are looking for so the report you submit will be acceptable. If they cannot produce one then it may not exist.

Just curious as to why you think you need this? I thought mains interlinked detectors - domestic style - were the thing for HMOs and I am not aware of any certificate.

Nice. I will now be able to feel good at the thought of you soaping yourself steam free.

Here is one Vent Axia did for a project for me. All the showers have extracts over.

I would want the unit to run flat out if I was having a shower. I would have thought that having it nearer the source would eliminate it more effectively, like having a kitchen extractor above the hob. Also, the vent pipes in the house would have a fair through flow of air and I would think that the internal surface of the ducting should be well above dew point. I wonder if there is any proper science behind this? @Jeremy Harris surely cannot be wrong!

Did they give a reason? I would be interested to know.

Shower room vents are best directly over the shower area.

I would think that if all the materials are clearly visible you could just supply photographs. Be aware that asbestos is often hidden away in soffits, stair nosings, floor coverings, pipe insulation, gutters and downpipes, boilers etc so unless it is clearly just brick and steel you should have it surveyed. Should be cheap to get done.

The photo was just copied from a website https://www.marazzitile.co.uk/collections/treverkheart/ but I have not used them On our roof terrace we have some 20mm thick porcelain on adjustable feet but not wood effect. Allows the water to drain away.

You will need a decent tile cutter. Also, it may look better if you perhaps have a 150mm perimeter tile upstand.

I have used some supposedly overpaintable stuff and the paint grins through. Have had to use a coat of Cover Stain to stop it.

Do as @PeterW says with the setting out. You could fit the hangers to the plate first, to save doing it in mid air. With the resin, drill the holes 14-16mm dia and 60mm deep if 100mm blockwork. Use M12 studding. Really clean the holes well. Insert the resin gun to the back and withdraw as you inject. Insert the stud and wind it in anti clockwise. Make sure your studs do not clash with the joist hangers.

Umm the pair of fleshy looking things under the coffee table...

And you need to register for CIS and VAT and unless you let the whole project to a main contractor (which may mean no profit for you) you will need to know CDM Health and Safety regulations as you will have a formal role as Client, Principal Contractor or more. You will need contractors all risk insurance. Unless you are experienced in the construction industry this could be a real ball ache.

This kind of thing but the legs are extra

Easy to do and very effective with a wood effect porcelain tile but far more tricky with timber, where it will fade to grey when exposed.

I am with @SteamyTea I know you have posted a few similar questions but I think if you are a first time developer now seems the perfect time to lose your shirt on this project. You would need about £165k cash and a track record to get anyone to fund this.

I think he has sold his digger. Let's not give him more work. The trench will need filling in any case and there is a mile of fall on the garden and sh!t does not flow uphill. It can probably be backfilled with the as dug and compacted to the correct level without any great harm. Maybe use a trench compactor if there is a lot of material.

I have had stuff rendered with just basecoat and mesh, rubbed up to a sanded finish and painted. Used Weber LAC. Excellent.

Where is all this escaping water going to end up? I think sand cement and build up a collar round the pipes will be enough. If it is many gallons of water it will escape somewhere anyhow.

Is there no way you could widen the existing access? I think a new access over common land is a no-no.