Mr Punter

If you will never need access, I don't see why it would matter. How does the cellulose stay put when it is installed?

Well I could not view the image or the vid, but you need to put patination oil on lead to prevent the oxidizing.

The corner beads look rusty. The top plasterboard has a sag on the left. Better strip it back, re-board, skim and paint. Quite a fiddle but not your problem.

You will want the screed to cure and probably bond to the concrete, so a dry slab may not help. The concrete may need some prep.

Yes, just stick it back on with adhesive from a mastic gun. I would not bother with dowels etc.

OK sign the form without amendments. What you have in there is broadly the same as was specified. Do you need to provide photos?

If you amend it the house will fail and you will need to spend ££££ on PV to get a pass. That said, solar PV is quite useful. It could still fail on fabric efficiency.

Rockwool is very good at sound attenuation, so no surprise there. You may well find that once the EWI and cladding are completed and everything is properly sealed, the issue will be resolved.

Can you post an update to let us know what Norrsken propose? They seem very well regarded here and elsewhere. Bear in mind the Marmox type board on the reveals won't help block out noise. I take it that traffic is the issue?

Is this a lamp or the whole fitting? Picture may help.

Yes I think OSB with a coat of solvent based varnish would work well. Apply to the edges as well.

I have found plywood to be a great home for mould, especially outside or in damp conditions.

No. VAT is payable and not reclaimable on appliances.

Make sure the worktops cab, if needed, be made deep enough to be able to route waste pipes etc behind appliances. Quartz are popular and work very well, but pricey. Ikea units are now a total pain to fit as they do not have a recessed back and there is only 80mm under them. I have used DIY Kitchens and found them OK for price v quality.

No. Unless there is an inch of render on the boards. A lot of stuff comes off when they are flipped over.