Mr Punter

Unless this is a strict planning condition you may find render is more acceptable to future purchasers and lenders. Probably cheaper and quicker as well.

I don't think you have misread. It looks like a thin coat render onto mesh on carrier board, so probably 6mm thick. God knows what has gone on and what to do. I would go back to the architect and ask for their suggestions.

On the drawing the flashing is not long enough to cover the top row of tiles. Having a roofed canopy addition on a timber frame with a rendered finish is always going to be very tricky to sequence and detail. It looks like the architect put this in the Too Difficult pile and left it for "others" to mess up.

You could use 82mm soil pipe to gain an extra 28mm. Plenty of fittings available. https://plasticsuppliesdirect.co.uk/soil-vent-systems/82mm-push-fit-soil-vent-pipe.html?p=2

You cannot join a WC in a Y. You will need ICs. These are best outside the footprint. Why the soil pipe in bedroom 03? As above, you need to work out your levels and take it from there. Design the runs as shallow as possible with a fall of 1:50.

I like medium density aggregate blocks, like Hemelite. They are a bit lighter than dense concrete and they cut more cleanly with the bolster. Easy to plaster and render and can be used underground. They won't help with u values though.

Yes, you are both right. They are so similar to Velfac, plus made in Denmark, I assumed they were the same group.

Yes. I have used their inward and outward windows and sliding doors. I have not seen / used Pure View. The 2 firms are part of Dovista group who also do Velfac and Velux.

I can't see a pumping station costing as little as £1k supply and fit. Good luck when it fails (which it will). New connection or RC slab over pipe.

Option 1 may need a DPM. You normally put a thin sand layer over hardcore to cover the sharp bits before you lay the DPM. Is foam glass expensive?

Concreting is one of the least forgiving trades on site. For a house slab it is not worth the risk if you are a novice. Spend some time finding a decent gang to do this.

How it normally would be is over fascia vent nailed to the top of the fascia, plastic eaves protection tray on top, supporting the felt and taking water into the gutter. Like this: I don't think wind driven rain would go up the fascia and through the vent, but I guess it could happen in a storm.

I can't see why not. It may be a fair bit more expensive and although it is self compacting, it will not necessarily be level. I would get a decent concrete contractor and use standard concrete.

The distance back from the kerb depends on the road type. The gates take a while to open, so you don't want to obstruct traffic. If the gates are over 1m high you will need planning consent.

Why is the "after" photo 4 years old? Take a new one and post it up.