Mr Punter

Most of the dry ridge systems will work fine. You can often re-use the existing mortar bedded tiles if you can get hold of a few spares to replace broken ones. You just screw battens to the top of the ridge to get to the required height and use this for the fixings for the ridge tiles. Easier than messing with mortar. https://redland.co.uk/products/components/ridge-systems/continuous-ridge-system

Can you add some timbers for the overhang on the top of the roof joists so they line up with the top of the insulation, so 120mm insulation and 120mm overhand pieces? Then bring the wall finish up to meet them. You will need to insulate around the timber outrigger pieces.

Aerated blocks are more prone to crumble and not good for fixing to or plastering. Medium density aggregate blocks are good allrounders but you lose a bit of insulation. It may make no difference to the bed reinforcement requirement but best to check with the SE.

The issue is that your floor level should be at least 150mm above the external ground level. It looks like it is the opposite. Also the ground level banks up from this. You effectively have a semi basement without proper waterproofing. If you are concerned whether the patio slab is providing support to the wall, dig a trial pit on both the outside and the inside. You could also gauge the water table from this. I once had a house with a cellar with a screed floor over a DPM and during intense rain water would force its way up between the floor and wall. We dug a sump and installed a pump and accepted that the floor would sometimes be wet. A proper membrane system would have cured it.

I did not even look at this from a b.regs point. You may need sprinklers throughout and enhanced smoke detector coverage. I have also seen automatic fire curtains specified.

I have not done one of these. It may be useful to look at other approved planning applications and see what information they have included.

As long as the new DPM laps the DPC it will be OK but needs to be protected against damage. Is the Topflow Horizontal expensive? I would be interested to hear how the pour goes / any photos.

That looks OK where the beams are at right angles and plenty of space to put the vents in. How is it where they are parallel?

No

My favourite is Egger Protect 22mm T & G chipboard. For a forthcoming project the SE has specced 18mm ply to the upper floors as part of the structural strategy. Who am I to argue?

I like the design but it could prove expensive to build. Have you had it costed? It may be that a few tweaks before it goes into planning will mean you have something that fits comfortably in your budget.

The upper floor insulation is not a matter for building control as it does not form part of the external envelope. Just do the calcs for the ground floor. Others on the forum are not so keen on nu-heat and may give you pointers to better systems. You don't need to have concrete or screed, you could have a dry system that will accept any number of floor finishes but reduce the height build-up. I am assuming you have done the maths on ufh v radiators? You will lose less heat with rads, they are far simpler to install and you will save some ceiling height.

The continuous dry verge is a good product. Just a matter of ringing round to see who has any in stock.

I am afraid this is all too common. It is sometimes hard to believe how incompetent some firms are. Do as @SuperJohnG suggests and keep records of everything. It is no good as evidence to say you "lost count of the times..." Take photos and get separate costs from the follow on contractors for remediation. They won't bother taking you to court for the £5k, especially when you establish your losses to be £10k.

Could you suggest, a bit like @Dave Jones suggests, some fixed prices for various build stages, either labour only or all in? With the 10% they are claiming for materials to date, maybe suggest this could be paid at the end of the job.

It might be good to debonding wall starters and some compressible material where you join to the house.

My brother has a large detached house high up on a hill but with highly shrinkable clay soil. The foundations are piled 25m depth. They wanted to have an orangery but did not want to pay to match the piled foundations so went for a raft. The orangery looked fantastic and for the first 12 months all was fine, but then some of the doors would not open and eventually it started to part company with the house. He has now had the orangery demolished and is left with a patch of uneven ground and some scars on the walls where flashings etc were. For @Shez, if the clay is not too bad 600mm deep would probably do.

It may be worth giving Celcon a call. I have found that these sorts of blocks can be more prone to cracking than aggregate blocks so I would want some proper assurance, as will your engineer and warranty provider.

Yes. The closer should have a key on it. You can paint with blue grit and fix some stainless eml to prevent cracking.

I don't think they do rhyming slang.

Roofer always uses 1.5m. Cheaper and easy enough to fix. I doubt anyone want to fix the felt down in a strong wind. There seems to be plenty online.

I am no expert either but that looks a very decent job. I imagine the others can be cleaned up with a bit of acid but be careful of the window frames.

Another vote for the Marmox Thermoblock installed at the same level as the floor insulation on the inner leaf of the perimeter walls.

I get what @Bonner is saying. I have often seen MIs that say bed completely onto sand and cement, which is a right PITA with a 40kg tray in a tight alcove. Same tray can be supported on some plastic legs.

I don't believe what is labelled on a CU. I once spurred off a kitchen socket having taken removed the ground and kitchen fuses. It turned out the socket was fed from upstairs. Luckily it only cost me the time to rewire the fuse but I have been more careful since.