Mr Punter

I fitted one with a 3" pump to avoid issues with solids. The tanks are fairly cheap so bigger is better, but make sure you backfill with concrete. Our neighbours have a dual pump system and they often have breakdowns, whereas a single pump is far simpler, but also bad news if it fails. If in the event of a failure you could pump to a nearby drain with the replacement pump you would save a load in call out charges.

Looks like it was designed by Escher!

What is the outer skin? If it is brick you will still need DPC and 150mm externally. Even properties with basements have DPC. The level thresholds have a drainage channel in front of them and this helps prevent splashing from rain. Also it is windows and doors in these locations and they do not soak up water or stain like brickwork / stone. You can reduce the 150 to 120 without any issues as long as the surrounding surface drainage is properly designed. You can always have a doorstep apart from the main entrance.

If you have a ramp for wheelchair access you cannot have a sheer drop either side of the ramp, so you either need edge protection or a slope to the sides. Imagine you are approaching with your eyes closed, you are a bit fragile or a wheelchair / walking frame user and are not that familiar with the route, as that is who this is intended to cater for. The solutions vary widely from site to site. As per @nod submit your proposal to BC or discuss on site with them.

If there is enough fall you may want to have 400mm from FFL to pipe invert and this will allow for whatever manifold to be sunk in. 100mm screed seems a lot so maybe go 75mm with thicker insulation. The floor will warm up quicker.

Perhaps they need a turning area for bin lorries and emergency vehicles.

You did well to cut a straight line in that stonework. Must have been a nasty job to do, especially so low down.

Is this for flood resilience? If the flood risk is that severe you should look at locating the kitchen upstairs. If not, just go with normal units, where you will get a huge choice at sensible cost. Kitchens only last 15 years before they look dated, so if you get flooded, just chuck out the damaged units and buy new ones. If you have stone type worktop this can be reused if you stick with exactly the same layout. Other flood resilient measures would be where practical, to site all electrics above EA suggested flood level, build ground floor internal walls in concrete block finished in render, have ground bearing concrete ground floor, install a sewer non return valve in a 1200 diameter chamber.

Can't quite picture this but it is not advisable to leave a long capped off dead leg as water can stagnate in the pipe. Also, if you do a below ground connection, try to locate it so that if required in future it can be exposed and replaced.

A while back we were contacted by a firm who offered to get us Capital Allowance tax relief because we owned some commercial property. They sent someone round who did a survey of the building - a fairly poor 1950s office -and they calculated the value of pipes, wires, air con etc. and lodged a claim with HMRC. We only bought the building with a view to demolish but were able to claim tens of thousands in relief for works carried out by previous owners.

You need specialist tax advice here, not the opinion of us lot! It is quite an intriguing loophole though, especially for high value purchases. Oddly there is nothing to say your woodland needs to be anywhere near the house.

You will need mesh in the concrete and maybe extra density XPS. Could be a job for engineer calcs. They are often cautious to allow for things like jacks which can be a fair point load.

You could get one with a side opening door. Here is a cheap second hand one: https://www.ebay.co.uk/itm/Gaggenau-Oven-BO250-111-60cm-Stainless-Steel-Used-only-a-few-times-Immaculate/292725962883? Actually still fairly expensive, but fantastic ovens.

We have a washing machine on the second floor, bedrooms on the first and second. House is timber framed from first floor up but the floors are well spec'd. No real bother from vibration.

Looks to me that you will lose a fair bit of space in the airing cupboard and the room below. You still need to get the stuff to the airing cupboard and then carry it back up to the bedrooms. Unless the stairs are a very long way this seems fairly pointless.

Yes I think a plastic trim would be good as otherwise the rubber is quite vulnerable to damage. I take it you are planning to remove the flashing, clean the rubber, trim to size, stick to the wall, install flashing with sealant, adhesive fix 50mm black plastic / aluminium strip to close gap to paving.

Even with no internal walls, with a building 5m x 9m internally, 300mm deep joists will normally be fine. Allow another 60mm for floor deck, finishes and ceilings, so 360mm max for floor zones. You can find a calculator at https://www.jamesjones.co.uk/interactive-span-table The Easi Joist values are very similar.

The bed in the middle looks bonkers to me. If you move it back you could have a sofa / chaise longue / table and chairs / dressing table / study area or whatever.

18mm ply is acceptable at 600 joist ctrs.

It is safer to have the floor in as a working platform. If you later need extensive access it will be from the ceiling below.

12.5mm or I like 15mm which gives (I think) the same protection as 12.5 Fireline. I have recently used Knauf Soundshield Plus which is tougher than normal board and good for fixings. I imagine the dry lining firm got a good deal on it, as our spec was just for 15mm acoustic.

Does the installer have insurance?

The DIY Kitchens I have bought for seven houses averaged at £205 per kitchen unit / £2,690 per kitchen.

Perhaps apply to get the wording changed to "shall be covered using slate matching that quarried from a source within the National Park" What was the stated reason for the condition?

You need to find something to match and base your application around this. If you cannot find it you will have to go with the local stone.