Mr Punter

I don't think it is worth stripping the pebbledash if it is sound. You could remove any bellcast bead and strip of pebbledash that will throw the EWI out and make it up locally with some thin insulation. EWI is quite effective, especially if you improve airtightness and ventilation.

Just some breaks in the vertical battens will allow air to flow round.

Yes, what you have shown often happens but it is wrong. You need air to be able to circulate behind all the cladding and a path for any water to escape. The horizontal batten and top reveal of cladding on the picture will prevent this and potentially cause problems.

As others have said, this is a boundary dispute. How come you allowed the neighbour onto your land to demolish your wall and erect a fence? The dispute has nothing to do with the Council. You are barking up the wrong tree. Get legal advice as you may need an injunction or other action.

Beware. Many warranty insurers will have asked the builder / developer to sign to agree their rules of registration, which can include a clause allowing them to recover any expenses incurred from you. The excess is also often £1,000.

I would look at different fixings before you destroy part of the wall. Charlie DIYte has reviewed a few:

Swap the isolation valves for these: https://www.screwfix.com/p/jg-speedfit-15aptp-washing-machine-tap-15mm-x-3-4-/18908

There is rarely any difference in foundation depth between single and two storey but only a couple of trial holes will tell.

I suspect the OP is a lawyer.

It may be worth stopping all work, then applying for planning consent for a replacement dwelling. Your friend should be eligible for CIL exemption, as well as VAT back. The VAT and CIL need doing correctly as the rules are strict.

You can use normal wall ties with the full fill insulation boards. You need to really take care to clean up the snots and keep the cavity clean.

If there is a surface water sewer in the street than that may be the best option. Did you get 3 quotes for the £18,000? What is the soil permeability like (clay, chalk, sand etc)?

You should be able to do this without planning consent.

What about a piece of timber? 4 x 2?

You may be able to extend at the side if you set the extension back. It would be worth exposing the sewer pipe so you can see the actual depth and location.

What about piles and ground beams with beam and block floor? It may save time and money and it is widely used.

I think you may be best ordering in 2 hits. The supplier may not want to be held to a price for a future order. If they turn up before you need them they will get in the way and could be damaged.

No issue with what you are suggesting. Sometimes the permanent live is wired to the switch, sometimes to the fitting / ceiling rose.

Yes they are upside down, inviting water into the cavity. A right fiddle to replace.

Maybe they are busy with other customers? It can take a while to get design information together. If they are a one man band they may not be able to respond to emails, texts and phone calls. Did you get other quotes? What does your architect think?

Drained ventilated cavity, much loved by warranty providers. Other than that, none I can think of. No, up to 80. Many over 100. You would need to price it up. I have not found brickwork to be expensive v. cladding. I imagine there are a number of wall tie options, either embedded pre-pour or post installed. This would be one for your engineer. Not really. Fibre cement and ali have coatings that deteriorate.

If you have room on the foundation, brickwork or rendered blockwork can be cheaper than cladding and should meet all your priorities.

A small amount of water ingress where you have a high water table is standard. Some of the plastic chambers have rubber seals that can be fitted between the risers, but they can be pain to fit. Regarding heights, it may have been best to have proper drawings based on a topo survey, with heights and inverts marked, but you would probably be up for an extra £1.5k in fees. Since the IC is between the back of the garage and a hedge I don't think it will matter. Also, better higher, so it does not become buried in the undergrowth should you need to access it. It may be worth you suspending work and employing a surveyor or site agent to do a fortnightly check in a Clerk of Works type role.

The weight of the frame is mostly resting on the 200mm polystyrene. You could extend this or move is outward by 74mm and finish with the same ali sheet you propose elsewhere.

I can't work out what the materials are. What are they where you don't have a door?