Mr Punter

Nice outcome. It is fairly common to see applications to have conditions varied or removed. Feel free not to reply but I would be interested to know how much were the fees for the planning consultants?

You could paint a white "cat runway" I suppose

Trench sheets can be hired. Again I would make this the responsibility o the groundworker to do.

I think you would be better leaving temporary works design to others as it is potentially high risk and you are not skilled to do this. You could expose yourself to all sorts of issues and CDM would come into play.

In your other thread you were looking at sleepers and I suggested this could be achieved fairly easily with no drainage issues.

Yes. Running to a gutter or just outside is better than an internal foul drain as you do not need to rely on a water trap to stop smells getting in. It is only the condensate from indoor air, so not corrosive.

Could you stick on a bit of stainless steel? Maybe fill sand and paint the end?

I have not seen the whole design. How is the fall achieved? I cannot see any firrings. Often the adhered coverings need OSB to be stuck onto and there is none shown. I am not sure you could fix EPDM to Celotex. I sometime see the tissue faced insulation specified but it is very costly. I would make the upstand out of 63mm x 38mm treated cls with 9mm osb sheathing nailed to the outside, insulated with 50mm Celotex. Be much stronger than the tile batten and better insulated.

I fitted Airflow Icon fans with delayed start timers, so they do not come on if you only have the light on for a short visit. They do a mixed flow one which will easily cope with a long duct run. You can duct through the ceiling or surface and box in if the joists run the wrong way.

I am not sure what your threshold detail is, but I would expect the EPDM to lap up the 30mm at the bottom and almost into the room. The cill should be well bedded down on mastic and sealed to the EPDM. Even if you do not have much fall there is no reason water should be getting in. This seems like a combination of poor design and detailing and poor installation. If the water is coming in through the door, remove it and fit it correctly.

I would avoid damaging the cavity trays when chasing in the flashing. The very small amount of residual exposure on a rendered wall will not be enough for any water to penetrate. So the left hand looks good.

Really you need professional advice on this. Have a browse through the VAT section https://forum.buildhub.org.uk/forum/174-vat-reclaim-queries-guidance/, but pub to resi VAT rules are beyond a bit of light reading.

Hi and welcome. There are some complex VAT rules on conversions. Be aware of time limits on the sale for SDLT. Are you going to be hands on?

I have done sleeper retaining walls with C and I section (PFC and UC) structural steel and sleepers slotted between. No trench needed. Sink the steel at least 750mm in the ground and concrete in. Use some terram or similar membrane on the back of the sleepers.

New build is often cheaper per m2 than conversion. Obviously a lot depends on how well the current building is constructed. A fair few commercial buildings have far better spec foundation and structures than dwellings do.