Fancy planners dictating window colours on a development like that. It's hardly likely the builder would do anything crazy anyway, they want to be able to sell them. One reason of many this country is knackered some office jobsworth dictating window colours.
If your not confident marking and cutting for the underside. Just use your jigsaw with a downwards cutting blade and take your time. It won't be a perfectly straight cut but as above the edge of the sink will hide a lot
Ah I understand i had manifold in last place worked well. If your cylinder is in airing cupboard and you have a separate utility/ plant room i suppose you'd have hot manifold in ac and cold in utility/plant?
Was that a typo in your original thread about australia? All their loos seem to be connected on a flexible with a tap on the wall. Must be some kind of reg over there? Here a lot of our toilets are plumbed in with fixed pipes. Even my old concealed loo was done with fixed pipework IIRC. Is there a reason they have to be on a flexi? Presume its too hard to change now.
I think OP said he was restricted to 350mm total due to foundation. My point is by the time you spend upwards of 2k on 25mm pir, 25mm battens and lose 50mm of internal space it doesn't seem economical
I'm with you I've never used pir in cavities either. I've done traditional with dot and dab and got great air test score. Parge coat prior and linked to airtight membrane on ceiling. I don't see how the pir helps you with this?