Mr Punter

I doubt you need to close the cavity in any case, but I would look at a Rockwool sock compressed between the wall plate and the outer leaf, resting on the wall ties.

Best drink it quickly anyway, just in case.

The green line would be your gas membrane, laid flat with no folds or laps, supported on the slab and external walls. You can add whatever other DPCs you may need, safe in the knowledge that the gas membrane is continuous save for correctly detailed service penetrations.

So can't you do this?:

Why have you lapped it up the brickwork? Just leave it flat.

Our guy used 4:1 with some fibres chucked in. Get the levels around the edge then fill in the middle.

I have never seen these. If you are doing a DPC cavity tray around the perimeter you could just lap any joins, but probably not have any other than change of direction. You could use some double sided DPC tape if you are feeling really keen. Who specified these? Is it a radon thing?

You may find it useful to get some measured plans of the existing building and site and any proposed new layout. That will make it easier to specify what you want. Do you want to improve insulation, ventilation, heating, hot water, solar, cooling etc? These are worth considering early on. £250k sounds a healthy budget but windows and external doors, kitchens, landscaping, automatic gates, wrap around balcony and glass balustrading can eat through a lot of cash.

Hello Hayden and welcome. The house looks a bit neglected. It is quite unusual being 3 storey with the integral double garage. What changes are you considering?

If they were cut to size that sounds like good value.

I have an early Victorian rental and the plinth in the kitchen is out by 50mm over 1200mm. Oddly it is not that noticeable to walk on.

We used to have several of these in Brighton, back in the day when stripped pine was in fashion. They would certainly be OK for doors and frames but I imagine the beams have to be done in situ. I would stick to the paint stripper. Work out what area you can do in, say, 2 hours. As least you will be able to estimate total time needed and progress, which might make the job seem more manageable.

Does the building suffer from damp? The render was probably added to reduce moisture getting through the wall and I would expect it to get damp when this is removed. For IWI, have a look at CharlieDIYTE. I like this method. https://charliediyte.co.uk/blog/blog/the-best-wall-insulation-for-old-properties

It could be better as a ridge beam on a low pitched roof.

The patio is too high. Raising it has made it even worse and he should have known better. The wall looks very damp. Could you form a channel next to the wall around 120mm wide x 150mm deep to act as a French drain?

I like the ball valves with a handle. You may need to adapt to copper first. The old screw down stopcocks can seize and leak. We have about 8 bar pressure at home and have a pressure reducing valve as well.

Glulam will be deeper. Price up in both.

Looks good for haunching up kerbs etc. Tossers.

They look good. I guess that at about £5 each, they won't feature for most plumbers or builders, but may work for high end projects and self build. I think tracpipe gas pipe is a bit like this, but it has a plastic outer sheath.

+1 for a couple of dMEV fans. You could also have humidity trickle vents or through wall vents for fresh air. Get rid of the tumble dryer and use a decent dehumidifier with plumbed in condense. Put a drying rack or rail in the same room / cupboard as the dehumidifier.

Yes. Don't have plasterboard as a strip either side and waistbands in the middle. Make the plasterboard L-shaped or e-shaped if you can and you won't get cracks on the joints.

This old garden wall had ivy growing in / on it. It did not do it much good!

With some of the Rationel frames you can couple them in a stack. Have a look at their install literature or ask their tech dept.

Fit a shower pump into the cylinder cupboard. Single impeller if your cold supply is mains pressure, twin impeller if it is a cold water tank. The negative head ones have a small air chamber that pressurises when the flow stops so the pump will be ready primed.

You seem keen to get a report from a SE. Most will deal with this competently. Let us know what they say.