Mr Punter

Gosh @Sue B that budget is a major challenge. Lots of work on the design side can really help keep costs down though. Try not to get wedded to a particular build system at this stage. As you know, the shape and form of the house can have a big impact on build costs.

NHBC provide structural warranties, which are required by most lenders. There are other structural warranties available from other providers that are aimed at self builders, so you do not need to be NHBC, just signed up with a warranty. LABC have one, but shop around.

Just to clarify, do you propose the windows to be white and only the front doors and the bifolds at the back to be anthracite? Was there a condition in the planning consent that asked you to submit materials samples for approval? If the answer is YES to the first and NO to the second I would just carry on and fit them as you suggest.

If you can't bring the whole wall out, just do the side up to the front of the shower tray. I will look OK when tiled. If you just extend the tray at the end you may have issues with the shower screen not fitting.

What, no WC?

It looks as if the wall is all on your land and between your boundary and the road is a pavement. I am not sure what you want to achieve - privacy, daylight / sunlight, additional usable outside space, security, kerb appeal? If possible, discuss with the planning office. You could probably have 1m high and later add trellis on top.

https://www.toolstation.com/forgefast-multi-purpose-self-drilling-wood-screw/p34893 any good?

Depending on the external finish, you can either use a mastic seal or Compriband expanding tape. The benefit of the Compriband is that it allows vapour to escape, provides a weathertight seal and allows for timber expansion / contraction. It is expensive though.

Do an application for removal or variation of condition. The fee is nominal. If your application is not successful they will need to give a good reason and you will be able to appeal. The PD Rights condition can normally be justified if the site is intensively developed, which yours clearly is not.

Looks great, as does the paving. Are they light wells at the front?

+1 to @PeterW it is there for site visits, not to indicate the visual impact of the proposal.

I think you could manage on your own as long as you have a lifter and a decent tower. A lot of up and down though! Assembling the tower single handed is a pain, as are the rest of the jobs. Maybe plan it so you lift up a board, screw one end, come back down, secure the other end with a prop, lift the next board, screw two ends at once. Although it is strictly banned, it is so much easier to get someone to carefully move the tower while you are up there.

No such general rule although some adopt a guideline for window-to-window distances of minimum 20m.

Can you get them to scrape just the very top 100mm off the drive and house footprint and pile this in the other area? Then they can do the rest of the reduced dig and muck it away. It is nice to have an apron around the house about 1.5m wide with hardcore for scaffold. Hopefully we will have a nice dry summer and you will be able to come to site in your white linen suit!

A VCL is impermeable to vapour and water and can be fitted to the inside (warm side) or the insulation. This reduces the risk of warm moisture laden air migrating through the fabric of the building and possibly condensing within the structure. A breather membrane is rainproof but allows moisture to escape and is normally located on the outside (cold side).

Wow - looks like a crime scene!

A fly screen mesh is recommended, although if there is sufficient ventilation up through the cladding it does not provide a good environment for bugs and flies.

You should have vertical battens fixed to the timber frame studs, then horizontal battens on top to help create air flow behind the cladding. A is better in your example as you need to make sure any water is directed away from the window head..

If both the FIL and you will end up with houses worth £500K would they consider gifting you their house? They could remain in residence but you could apply for a new mortgage on their house to finance your build. In the event that they live for seven years, no IHT is payable. There is no SDLT either. If they require Local Authority care they won't need to dispose of the house to fund it. It may be a bit controversial, but I think it may be worth looking at.

Not as a structural upper floor, but you can have a screed or use ScreedBoard overlay.

I doubt you will get a decent ring beam without form work. Have a look at

Although you mention some kind of screening, I think the house will suffer badly from overheating, especially in the afternoon. This is best designed out now, as it is very difficult to deal with later.

Brick clad first floor and timber ground floor is unusual and timber is not great near to ground level. Is there a reason for this choice?

Powder coated aluminium? Pre patinated zinc (expensive)?