Mr Punter

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.

He will probably be fine with plastic fittings and IC. Much simpler.

Plastic inspection chambers are not designed for steep gradients so you may need to build one to suit. Talk to your groundworker and to BC. What depth is the pipe?

A friend does automatic gates and access control. He cuts a wire loop into the driveway which seems to be a favourite. Why on earth would you want to tie your automatic gate functionality to a particular manufacturer?

+1. May as well heat it with the car exhaust!

Why not just shift the fridge elsewhere in the kitchen, tile where it is to go, then move it back?

Agreed I have heard this claim but cannot see it in the Building Regs.

You will need mechanical ventilation in the kitchen, bathroom, WC and utility. You also need trickle vents to all the habitable rooms. The fans may need testing also. What did Building Control put on their Plan Check report?

I like traditional sand cement screed. 75mm is quite thick for liquid screed. If you go liquid, use Cemfloor as there is no laitance removal needed. I have used Sigma Screed in the past and they were very good.

I think you need check reveal cavity closers as one of the wings will clash with your brickwork. These https://insulationgo.co.uk/150mm-xt-cl-close-r-checked-fit-pir-cavity-closer-brick-outer-pir-core-insulation/ or if you want fire rated, which may be a better fit with the rigid insulation: https://www.insulationsuperstore.co.uk/product/arc-ecocloser-150mm-fire-rated-cavity-closer-2-4m-length-pack-of-6.html