Mr Punter

If you have internal load bearing walls the hollowcore planks or beam and block would work fine. A well designed timber floor can also work very well and would meet your criteria, additionally allowing a greater choice of structure type. It is best to get an approved design, then decide what performance you require (insulation, low noise transfer, construction speed, maintenance, durability, environmental impact, price etc.) before deciding on structure type and build method.

Where is the insulation? I suspect you may need to strip the lot and start again. I am not a fan of the central drain. Unless you get this properly designed you will be messing about forever.

The only approval you need is for the replacement beam, floor joists and insulation (fabric improvement). They may not like the current layout, but tough.

If you have not made any changes other than even up 2 rooms, you don't need Building Regs. If you have, for example, removed a corridor or moved the kitchen it could be required.

To be a fire refuge I think it needs to be deeper than the building is high. If it is existing and no changes to the house I don't know why BC are interested?

I think you will need to be very hands on to get this done for £40k. You can sub out foundations, brickwork, plastering, electrics and plumbing. You may need to do some carpentry, roofing, drainage, gutters, kitchen install, paving, tiling and decoration. I think you will need a Party Wall Award which will cost maybe £1,400. You need engineer drawings and calcs. Is there access through the back, like a tarmac road across?

Christ what a mess! I can't see how that could be patched in, but I have zero experience with laying microcement.

It is only an issue if the concrete remains damp.

I get it now. I would be a bit pissed off with the architect for designing an expensive feature that has now cost you more time and money to scrap / modify and leaving you to design the solution. It looks like there is still a wasted void to the left of the left-hand pier. That space would be worth about £2,500 round here.

I guess you have a digger on site and can source concrete in small quantities. You will need to consider moisture ingress, airtightness and tying the the blockwork into the icf. Is the block wall going to be cavity? Unless you want to DIY you will need a bricklayer. I am not convinced with ICF, blockwork and timber frame mixed on the same external wall but if it works, then fine.

You need to either lower the ground or cut the bottom of the cladding. The posts should be cut down and sat on a metal elevated post base. There is a fair amount of work to do.

I would say no but if it is part of a new electrical install you will need it all tested and signed off for part P.

+1 They do anthracite and black. Go for smooth finish.

+1 I can't see the point in building a timber framed business unit.

If one of the spacers is a bit high you will never get the tile level and will have the messy job of removing it from wet adhesive.

I read it as no sheds, kennels, workshops etc without PP. Quite restrictive.

I can't work out how you got such a good score (83) with such poor insulation. Do you have solar panels?

If you are outside a Conservation Area and there is no TPO or planning condition you can do what you like.

LABC foundation depth calculator:

I am not sure that the foundation is deep enough. 2.4m may be more like it. The low density polystyrene is heave protection and used on the inside of the foundation trench. It can be difficult to use as it tends to float in the new concrete.

No, the housebashers often have "Type Approval" style certification. Mostly the only things that get looked at are the paperwork. Site agents are more interested in RAMS from their subbies than build quality.

If the tiles are the right type you can lay them onto adjustable pedestals.

Stupid pop-up sockets?

What do you mean by this? If you have planning drawings that you are happy with they should be able to use those. You may need some input from a Structural Engineer for some aspects. If you want changes to the approved drawings you could get an architectural technologist to do these. If they are simple you can just mark up the existing drawings for your chosen timber frame company.

They should all be able price from planning drawings, without a fee. You will need to chose the spec you want.