ProDave

My concern is with the description of the depths and the sloping site, at the low side, you have barely scraped the turf off. Whether that is enough or not depends on what the soil is and how long since it was last disturbed, I would certainly be putting steel mesh in and pouring the concrete without insulation to get a decent thickness reinforced slab. Then build on top of that laying an insulated floor inside the building,

We used standard corner beads opened out a little.

Time to give Linux a try?

If I had a house like that, I would be fitting a new front door (pair?) right at the front. Making it a much more useful enclosed secure dry space for bikes, boots, coats etc.

I used 70mm duct (or about that size) after SSEN also told us some ridiculous size like 150mm. The guys on the ground are sensible. But don't do as one builder I worked with did, and installed blue mdpe water pipe. I can assure you SSEN WILL refuse to put a cable through that.

But don't forget the yellow warning tape to be burried just above the duct.

The new connection process is all now a bit disjointed because you can (have to) choose your energy supplier. So SSEN will connect the supply and the main fuse and walk away. You have to choose an energy supplier. You can do that before the actual connection is made as soon as they give you your MPAN (Meter Point Administration Number) Some time days or weeks after the supply is connected your appointed energy supplier will turn up and connect a meter. I think it simplifies the process if you choose SSE as your energy supplier. Don't sign up to a fixed term tariff. You can then switch to your preferred supplier when it's all working. If I were doing this now, I would have my garage consumer unit already installed and connected to a pair of Henley blocks so the meter installer just has to connect the meter output to the Henley blocks. Then later on when you connect the house, you have the Henley blocks to join to for the switch fuse to the house. When mine was connected, I chose SSE as the supplier because I know they generally fitted a meter that has a built in isolator switch. I suspect however today you will be given a smart meter. If so that won't have the isolator. Do please let us know if you are forced to have a smart meter or can still choose an ordinary one.

Fit a consumer unit in the garage, that can feed the garage circuits and the static caravan. Also fit a switch fuse to supply a SWA cable to the house when it is built. Here is my remote meter and consumer units I must take a new picture, that was before I connected the SWA to the house that now exits the bottom of the right hand meter box from the "main" switch fuse. All that SSEN are saying, in common with ALL DNO's is you cannot rely on their fuse for anything longer than 3 metre long meter tails. In this case the consumer unit feeds the caravan my shed and the site socket. the switch fuse feeds the house. The off peak switch fuse is not currently in use but is future proofing should I want an off peak supply at some point. In your case I would have a small permanent CU in the garage that will feed all garage circuits and can feed the static caravan and disconnect that when it goes. Remember the caravan must be on a TT earth not the probable PME supply you will be given. And connect a switch fuse with an 80A fuse in it (to give discrimination from SSE's 100A fuse) to feed to the house.

Build the whole house with a decent service void, mine is 25mm AV cables in before the plasterboard The finished result

I got the cost of my electricity connection down a lot by doing all the digging and laying a continuous duct, with a draw string. from the connection pit to the meter box. And I dug the connection pit and filled it afterwards. SSEN were entirely happy with that. all they did was pulled their cable through my duct and connected both ends of it.

I would think out of the box. Get the supply installed into the garage as a PERMANENT supply. Run a sub main to the caravan, and when it is built, another sub main to the house.

A relative pulled out of the purchase of a house once, because it was built behind another house, and the only access to it was over a bridleway. The solicitor pointed out he could walk to the house or ride a horse to the house, but he had no legal right to drive a car or other vehicle to the house, even though the present owners were doing that. If you want this access once in a blue moon to get something big in, I would just do it. But for regular access in a car I see no option but keep using the existing legal access.

This smoke etc on a still day is an interesting problem. We had an odd similar problem. One morning I came down and thought the house smelled stale, not the normal fresh air we were used to. It was a dead still spring morning with mist hanging in the valley. I went outside and the air outside smelled of stale drains. It was next door taking a shower, they still have a septic tank discharging into the burn (illegal now but no sign of them upgrading it to a treatment plant) and there was just not a breath of wind to take the foul smell away, and that was being drawn in by the mvhr.

A well built air tight house will be rodent proof. A mouse only got into ours when I was fitting a roof window and left it overnight with the window in but not sealed. We had previously hear the mouse scratching around on the roof under the roof tiles. Put poison down for the rats inside a tube near where they live.

Telephone TV aerials etc (mine enter under the founds and up into a cupboard via a hockey stick) "spare" at least one decent size duct into say the plant room for the "unknowns"

The "issue" appears to be you have already dug the step for a backdrop. So the problem now is filling it back in again and compacting it all if you go for the steep slope method. The time to have asked the question would have been before digging that deep (sorry)

Mine too was only specced for taped OSB3. but I decided to line the whole inside with an air tight membrane and used Protekt Barriair. The decision was swayed by the builders had already anticipated this and used air tight membrane to detail around the joist ends, something that has become known as a "Tony tray" around here.

There was a case here of an unadopted road serving 1 houses. When a third was applied for, they made it a condition that they update the detail and visibility splays where that unadopted road met the public highway.

Would a ballanced flue work for a WBS with the air intake right next to the smoke exhaust? When we had a 1930's house, it still had an open fire when i bought it, and due to the lousy heating system when I bought it, I still used the open fire sometimes. That house had a fireplace in the living room, another in the largest bedroom above, and a third (disused) pot that used to be fed from the copper. A quirk on a still day was if you light the fire, then it needs combustion air from somewhere, and there was no provision for combustion air other than "leaks". So it would draw combustion air in from the easiest place, which turned out to be the upstairs fireplace, down the stairs and under the living room door. On a still day with no wind to take the smoke away, it would draw smoke down the chimney and fill the bedroom with smoke. I think a concentric boiler flue works because it is usually fan assisted, which I have never seen with a stove.

Sheds / garages will never be rodent proof. One year I filled the lawnmower tank for the first time only to watch it all drain onto the floor. A mouse had eaten through the petrol hose from the tank.

No the external air only enters the stove, making the stove room sealed.

A stove under I think 4kW does not NEED an air intake according to building regs. I would however recommend buying a stove that has a ducted air intake. Our stove at 4.5kW has both it's primary and secondary air intake via a duct. In my case that duct draws the air from the ventilated space under the suspended floor. When the stove is not in use it does not create a draught and makes little change to the air tightness.

I use MDPE for outside taps. The building site standpipe never gets turned off and survives Highland winter freezing without issue.

Not at all a problem. Tapers have to deal with square edge to square edge on a large ceiling.

This "saves energy" claim has been investigated at least twice by the ASA. You will now note the footnote now to the smart meter advertising that you can only save energy by monitoring your energy usage and making changes to what you use. But lets be clear about that, it is NOT the smart meter that enables that, it is the energy display gizmo, and as already noted you do NOT need a smart meter to have one of those.