Mr Punter

Strip the roof and re-lay. You need MINIMUM 50mm into the gutter. They are fibre cement slates fixed with nails and disk rivets. You could sort out the rest of the woeful bodges while you are at it.

I have done similar using resin anchors to face fix a timber ledger to the wall, then timber to timber joist hangers for the joists. It means you have more freedom in floor height and better airtightness. Your blocks should be fine for this as the ledger will have fixings every 400mm. Cleaning the drilled holes with brush and blower is key to a very strong fixing.

I would just go ahead and do a retrospective if it crops up.

Don't pay them until they get it right.

A more important factor will be the loss in floor area, which if it is 1.9% on a floor area of 160m2 would be about 3m2, which could be worth between £6,000 and £12,000 depending on location.

I have had quotes for this before and they were very expensive to cover the whole house, but can be handy for smaller areas. Get a flow rate / pressure check. You can request a very meaty supply from the water co. just for fire sprinkler purposes. Have it separate from your main supply.

Yes, mineral wool is far better than pir for this.

The res bars are good call. Easy to fit as well.

I have no experience of them but if they are a decent fabricator and you have seen their installations then why not?

Only if he gets caught naked.

Why do you think you need a demolition statement? Who is asking for it?

Well you will be by the time it is completed! Plan it carefully. Incorporate drainage along the back and through the wall. Design depends on height, what it is retaining and aesthetics.

Your builder and their contractors should provide you with RAMS (risk assessments and method statements) for all hazardous works (work at height, demolition, lifting operations, machinery operations, manual handling etc.)

If it is for asbestos, the builder can get this done. What did they quote for?

This all looks fine to me. What is your concern?

I agree. Do you think the guidance is aimed at timber and metal frame type walls?

Yes it will stop the floor dusting. One watered down coat will probably do it.

Have a read:

How very odd. This sounds like a fundamental design issue as the two flows should not meet. Get a refund and maybe try another brand, like Vent Axia.

This does not apply if the wall consists of two leaves of brick or concrete, each at least 75mm thick. See "Diagram 5.3 Cavity walls excluded from provisions for cavity barriers" ADB V1 2019.

@ETC and @ADLIan are both experienced professionals and do not see eye-to-eye on this, so what hope do the rest of us have? Cavity closer, fire stopping and cavity barrier seem to get used interchangeably. I like the idea of @ETC's calcium silicate board cavity closer but Google does not come up with any. Mostly they are plastic with polystyrene or FR ones that are plastic with mineral wool. I can't imagine many bricklayers cutting up calcium silicate board on site. The lack of easy practical and cost effective solutions often leads to shortcuts and poor implementation.

I think that the terms used can be confusing as the words internal, inlet, intake, supply, external, exhaust and extract are used, sometimes interchangeably, to label four pipes. It can be even more confusing if these are abbreviated to Ext, Int etc. Having four readings on a cool day like @Dreadnaught has posted makes it easy to see what is being measured. I doubt there is anything wrong with the MVHR unit of the OP.

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.