Mr Punter

I would doubt it would cause an issue but maybe alert him to your concerns. Planting trees down the centre of a shared drive sounds unusual.

As per @Russell griffiths it needs to be non-climbable. Cover the top part in broken glass and razor wire to make it safe.

Maybe a 1.5 storey chalet style with pitched roof would be better? Can you get a sketch scheme done and have a chat to the planners? Make sure it looks good. If you made it, say, 6.8m x 6.8m you would have over 70m2 of floor space, 1.6m from the rear and side boundaries and be 21.6m from the existing house.

As above, if you are a self builder, CDM does not apply. F10 would not apply anyway. Make sure your contractors do their own risk assessments, are fully insured and supervise their own workers. If anything is requested (alter scaffold, supply electric etc.) make sure it is done but that is is still up to your contractors to verify that it is safe. HSE are not interested unless something goes wrong.

It can sometimes be a bit tricky to find room for these, especially with full height windows, doors, steel columns, wind posts and services. With your brick bond make sure you leave lots of space with a bigger lintel on the inner leaf.

With concrete piles they often do pile integrity tests to make sure there are no defects along the length of the pile. I think they connect a sensor from a tablet and tap the pile with a mallet. Somehow this tells them a fair bit. They do it for every pile. You may also need concrete cube tests.

I think it is good to have some DPC on the outer leaf wrapped around to the back. Other than that, @tonyshouse method seems to work OK.

I think they tend to work better if all around, not just opposite walls. 12 is not many and it would be a shame if BC picked you up on it.

Recessed would look best I think as you do not need it to be weatherproof. I like the way the coursing works in with the ceiling, cupboard and beams. Well done.

It may be worth talking to Building Control as they will probably be familiar with the soil type and typical pile type in your area. A Mackintosh type probe would probably reveal if the clay continues to full depth. It is a manual device and would be far cheaper to do. You can use the NHBC depth calculator to work out strip footing depth or whether a specialist foundation is required.

Some of the resin type stuff is rubbish if you drive over it. Worth overspeccing if it it taking vehicles, as delivery lorries etc may drive over it. The slot drain stuff looks very neat. Plastic stuff like RECYFIX PRO 100 is decent and will take high loadings if installed to spec.

You could DIY an overlay UFH system on ground floor only. If the house is well insulated you will not need anything upstairs but you could get a portable fan heater and use it for 10 minutes for the exceptional days. Heated electric towel rads on timers in the bathrooms. The gas combi seems more attractive though.

Yes but you are a sparky. Big ceiling with lots of spots and the plasterer will not thank you for covering it with holes.

It is a nice looking design. I like the dormer type windows, which I guess is vernacular style? Is the cladding brick for the rest? How do you support above the "extension" roof?

Why not leave them. Measure and mark carefully on a drawing, tuck the wires up so they don't get caught later and drill the holes when he is finished and after you have painted the ceiling?

One more bad work from you and I will send round some highly trained cats to crap in your garden.

There you go. Five minute job. What was all the fuss about?

I once put grey aluminium half round on a development. It ended up looking similar to plastic but was 10 times the price.

Nice, but expensive and may attract thieves. Does it go green or is it coated with something?

Looking very good and a great location.

I don't know why he chose to fit it on an internal join like that. Anywhere in the shower would have been fine... Still, it won't take a minute to move. Would you let the foam go off first?

Sorry I did not make clear there are 2 issues here: (1). You cannot have loose gravel getting on the road. (2). You cannot have surface water runoff from your driveway to the road. You could have a permeable bound paving or permeable block paving with special sub base and bedding which would solve both but is expensive You could have any solid paving to solve (1) and a linear drain to solve (2) I suspect your proposal to highways was for loose gravel, which would not solve (1) hence their response.

Liner drain across the threshold to the road piped to a soakaway, then you can use whatever you want. They just don't want runoff from the drive.

If ground conditions allow and the site is fairly level, a ground bearing slab is better than a beam and block floor. You will need a minimum of 100mm Celotex or 150mm EPS for the floor. Where this goes and what depends on construction type and floor finishes.

Doubt it will be under his breath. I bet @pocster tells the plasterer the boarding was by "others"!