Mr Punter

Blimey you have not had much luck with this, have you?

It is often good to have your own space and some 'adult' space where the kids / teenagers are not TOO close. Same for wrinklies, guests etc.

Can you not have piles, concrete ring beam, beam and block ground floor with brick and block ground floor walls and timber frame above? No issues with corrosion, fire protection or flood resilience. You could externally clad the timber frame walls in slate, hanging tile or cement weatherboard.

Rub with a dry bar of soap and polish off with a soft cloth.

They used shipping containers to house homeless in Brighton. Not cheap to do and not that popular. https://www.vice.com/en_uk/article/gq8jyq/i-spent-the-night-in-brightons-homeless-shipping-container-housing-project

If you have a decent job I would not advise that you give it up or reduce your hours. Better to improve your position and gain promotion / increase income. I assume you have looked at what you can get for an extra £250k? Have you done numbers on whether the work will increase the house value by at least what you are spending? I don't know why the architect needs to be involved throughout and paying a percentage may be wasting your money. Maybe post the plans and invite comments. There may be areas where you can save lots of money and it will make little difference to the end product. WRT planning consent unless you make changes to the externals it is unlikely that you will need to go back to them and it certainly would not be 18 months.

I think the gutter needs to be finished in GRP or similar and needs a min fall of 1:200 to the outlets. Make the outlets are lower than you think they should be as there is often a build up of material near them so the water does not drain. Design it so if you block the outlets the gutter will surcharge down the outside of the building.

Screw in from both sides alternate 50mm from top and bottom. 200mm ctrs should work fine so 10 screws per metre. More won't hurt. Screws not fully threaded are better as they pull the pieces together.

The search is correct. OK subject to ground conditions. No good on clay. My brother had an orangery add-on with a raft. The rest of the house was piled 25m. Clay soil. None of the 3 pairs of doors now open properly and he will probably have to demolish it if he want to sell the house.

Quite a small room! You can do the brickwork tomorrow but leave a day before the plate on the sleeper wall. When you do the wall plates you may find it easier to nail the hangers on first. The joists do not need to go right to the walls, you can leave 100mm and pack those gaps with insulation / foam.

In timber frame it is the horizontal timber - head binders, sole plates, joists, rim beams - where the shrinkage happens. I think these still exist in SIPs.

Yes, move it inward by 100-150mm. You will also need to allow for differential movement between the frame and the blockwork, especially at upper floor level, as the frame will shrink downwards and the blockwork will not.

But this does not have what @Triassic needs which is spec and detailing for fire barriers in ventilated rainscreen cladding

You should close the cavity (usually with 2 x 2) around windows and doors. This stops a fire in the house breaking through into the cavity. You could fix intumescent barriers at the top which would choke down the chimney effect in the event of a fire. They don't seem particularly easy to find or specify though.

Trouble is, if he closes the cavity the ventilated rainscreen cladding will not work as designed and he may get damp issues. The cladding manufacturer will show continuous ventilation top and bottom.

We had a 30s house with that style of door.

They are not had to get hold of. I have one I don't need. With three prongs. The security fittings I had were made of a different metal and tended to fuse to the bolts. I am in Sussex.

These are really good at stopping small children opening the door.

Never too late for you to dig it up!

CAT5e

I can never work out why UFH pipe runs always have a very congested hot 'corridor'. In your second pic there seems to be 7 pipes in 600mm. It looks possible to alter the design quite easily but maybe nobody can be bothered.

More like a continent than an island! Once the cabinets are all level and screwed to each other they will be fine.

I would concrete it. We once fitted a plastic tank in clay in dry conditions. Concrete base and just backfilled with shingle. The following year after it had rained a lot the sides and base were misshapen. The tank was plenty oversized so we filled the bottom of the tank with concrete to prevent if from collapsing but I would concrete all round if I had my time again.

Bear in mind if you have 2.7m downstairs you will need a couple of extra treads on the staircase.

You could have a bank of 300mm on the left hand side and I don't think you would need any on the right. Allow 1000mm width for the hedge and plant it 400mm back from the edge of the pavement, then slope the bank at 45 degrees. Grade the rest away from the house. You will want a fall on the patio of 1:50.