Mike

Indeed, BS 8300 isn't mandatory. And neither are most of the 'solutions' offered in Building Regulations Approved Documents The Approved Documents mostly contain 'deemed to satisfy' provisions, but if you can justify another way of satisfying a 'requirement' to the satisfaction of your BCO, then you use that instead; the Documents say that themselves (see the section "What is an approved document?") If a British Standards offers other solutions, then that is (very) strong evidence that you can provide to your BCO (and boss) to justify what you want to do. As may any other reputable document or guidance.

I don't recall seeing a part M toilet with a seat. If you can get hold of a copy of BS 8300 (through your library, maybe), that may give some other options.

I know the feeling! I design all bathroom wall elevations in CAD - tiling, niches, sanitaryware placement, door handles, shower controls, towel rails, lighting, extract...

You don't have to mount them in a worktop - hang them on the wall or stack them in a rack instead: https://www.fabita.it/en/products Or inset as many or as few individual induction plates as you like, from Foster: https://www.fosterspa.com/en-ww/modular-induction-7366-020.aspx?ndomain=6

A good idea. Do a Google search for 'appliance garage' for some related ideas.

For wall cupboards, you can get pull-down shelf units to bring everything to hand. Also, it's not necessary to have 600mm deep units everywhere; it makes sense under a worktop (though you could skip that and just have a table), but elsewhere do what you want. And a pantry for food + a walk-in store for utensils & crockery is great, if you have space. Or skip the worktop and use a boat instead? https://ashgrovekitchens.co.uk/case-studies/ship-ahoy-in-exeter/

That's waterless trap and the hump is normal. The pipe should, however, still be flowing downhill - it rather looks like it's flowing uphill; if so, that would be a fail.

There will only be one pair of fans (one for supply, the other for extract), but they can both run at 3 different speeds. Speed 1 is for when the house is empty, 2 is for normal use, and speed 3 for boost. The installer should have set the dials to move the correct amount of air for each of these speeds to suit the design, which takes into account the layout of your flat. Presumably you have a controller that can switch between all 3 speeds, as well as between summer & winter - so 6 possible settings. If you can measure how many Watts it uses in each of these 6 settings, then that may provide us with some clues.

No, you don't need fire doors if you're converting the loft of a bungalow. Building Regs Approved Doc B1, section 2.21, requires fire doors only "where a new storey is added through conversion to create a storey above 4.5m". My guess is that they've copied and pasted from a previous job.

Traditionally it would have been run in plaster using a profiled sledge. I found a video of the technique for you, though the quality is low - see below. Not sure about running it in pure casting plaster though - it may be too brittle. Normally fibres are added for mouldings, but on a wall probably just fibre-reinforced lime plaster, at a guess. It's not something I've tried, but if you were to use a double layer of plasterboard and leave the second layer short of the corners, in theory that would provide the space. Try some experiments...

There is absolutely no problem with MVHR in a flat-roofed building, just as it can be installed within an apartment with no roof at all. The entire installation is ideally installed within the heated (or cooled) building envelope, so you just need enough height (or other space) to run the ducts. Maybe Google is showing pitched-roof houses as those are the buildings into which it's mostly installed / the owners who would most often choose to install it. In view of the dust, I'd make sure that you have some good-sized pre-filters ahead of the actual MVHR unit, so that it's not necessary to change them too frequently.

The big installer of high WCs is the NHS, whose WCs always seem uncomfortably high, though no doubt OK for those with mobility issues. If they're all to the spec on page 87 of this document, they're at 475-480mm. You could call in at your local hospital to 'test drive' one. BTW, in terms of ergonomics & health, squat (or low) WCs are said to be preferable to the standard Western model. See, for example, https://www.ahealthylife.nl/wp-content/uploads/2020/07/Straining-study.pdf

And, in addition to the set point question, the User Guide also indicates that there's a manual switch to select either summer or winter mode, and that "Selecting “Summer Mode” means that the MVHR will target a lower internal temperature during the warmer months." If it's currently running in Summer Mode it would be fighting against the heating system, which may also explain the power usage.

I am :) It's cold enough to turn on the Willis heater UFCH tonight..

And now in infra-red (thanks to my new toy) The value's not shown here (due to the insulation), but the water coming out of the top of the active Willis is just under 44C.