Mike

Maybe that's the time to turn it on then - keep the vents in the areas you're not living in well bunged up and go for an initial approximate balancing to suit the areas you are living in.

it's realistic enough to have spent several hours successfully doing it myself. Even a tiny hole in a high wind feels like someone's blowing cold are down a straw at your hand - no candle required :)

It can identify where the main air leaks are so that you can fix them. I'd rather do that than rely on Aerobarrier at that stage. High winds make for a good pre-pre-test (or post-test) too; go around all the junctions slowly & feel for air leaks & mark them or fix them on the spot.

Yes, I've seen that happen and adding insulation will resolve it. Be very cautious about running the MVHR - as @JohnMo says, you don't want to be drawing dust into the system. However it is possible to have it running when there's no work going on if you take some precautions & accept the risk, as I have. While work is in progress and until dust settles, keep it switched off; during work put plastic shower caps over the terminals; add sock filters to the extracts (a good idea anyway). Also consider upgrading the MVHR return air filter to better protect the heat exchanger - from (normally) ISO 16890 Course (old G4) - to ISO 16890 ePM1 (old F7 & as normally used on the air intake), which filters out at least 50% of very fine dust and 85% of medium-sized dust (up to 55% of sawdust, for example, is too fine to be trapped by a course filter). I've not done this myself as I suspect that these smaller sizes (<10 microns) would be fine enough pass through the heat exchanger without building up significantly, but I've not looked for any research on the topic.

It's a good point. From memory, the surface tension of water droplets requires a hole >6mm diameter for the drop to enter. Foam pipes will join together closer than that, so the risk of individual drops entering the joint is low, so long as they can run down the duct and not accumulate, so I'd say that the risk was low. Low enough for me not to worry about anyway

Taping isn't normally essential (unless part of any Radon protection), however you have a special case because - from the architects drawing - the DPM level is at external ground level and there is therefore a much greater possibility that damp (or even water) could pass through from outside into contact with the DPC. I'd therefore want it well taped to be certain that it remains dry. 150mm horizontal overlap is fine, but it doesn't look like you have 100mm vertical overlap though; you'd need to increase that with a bigger piece of DPC to meet the Regs. BTW, were the internal wall sole plates preservative treated by the frame manufacturer? I'd have wanted them to be (and TRADA recommends it), so if they're not I would attempt to apply some now, maybe using the DPC as a temporary tray to allow some to be poured & soaked up. Due to the internal wall sole plates being located (eventually) in an trough insulated at the sides, separated from the uninsulated concrete by only the DPC / DPM, I'd expect a somewhat elevated risk of condensation. I'd prefer it if the polythene was above the DPM, as the DPM will better resist any damage if it gets pressed against a sharp edge in the concrete - unless you have a mortar bed underneath that's preventing that? If the polythene were to be punctured there's a risk that the distance from puncture to the edge of the overlap would be less than 100mm (due to the 50mm DPM projection), so another reason to at least tape the joints. But, with all of this, it's your BCO who has the final word.

Sheltered under the eaves / gable & with no brickwork above, so no dripping water even if it the inner face gets wet.

I suspect that they will, but you'll have to ask. While it may be a garage, few garages these days seem to get used for parking cars - and whatever it gets used for instead may be disrupted / damaged if rain does start dripping in.

In the context of the Crown Estate, give its assets to a Quango / Government Department to run? An excellent idea in principle that could be done right away by hypothocating the relevant profits. Though maybe the Contract for Difference subsidies (£1.9bn last year) exceed the revenue?

It is, and it is a strange arrangement , but the percentage does get reviewed from time-to-time - currently inflated to contribute to the refurb of Buckingham House - projected total £132.1m for 2025-26, it seems. Here in France this year's budget for the Presidency is €125.66m, and for that we only get one person royaling / presidenting. You might not save a lot by returning to a republic :)

The Crown Estate is not the private property of the King. Our assets are hereditary possessions of the Sovereign held ‘in right of the Crown’. This means they belong to the Sovereign for the duration of their reign, but cannot be sold by them, nor do revenues from the assets belong to them. The UK government does not own The Crown Estate either. Established by an Act of Parliament in 1961, subsequently amended by The Crown Estate Act 2025, we are an independent, commercial business, managed by a Board (also known as The Crown Estate Commissioners). ...we continue to give all of our net profit to HM Treasury for the benefit of the nation's finances. https://www.thecrownestate.co.uk/about-us/faqs

I'm not aware of a better way. If you use adhesive and clamp it up with the bolts it should be resistant to movement and there really shouldn't be a build-up of muck.

As per my post above, yes.

Exposure extent, rain quantity, rain duration, wind speed, brick permeability, quality of the mortar joints, low height of the wall...

Some of the work of a company I worked for was fixing NHBC insurance claims. One of them was retrofitting cavity trays that had been omitted by the original builder; stage 1 of that was cutting out bricks to verify the cause and identify the extent of the problem, so I've seen myself just how much can get through - a lot. Never omit cavity trays.