ProDave

I have never heard of anyone needing a 700L hot water tank. I would be questioning whoever specified that. How are you heating the hot water?

I can't recall the rise and going of mine, but the rise is close to the maximum allowed under building regs. I had to fit the rise into 13 steps as it deliberately had to be offset, if both flights were the same, the bottom step would have been in front of a doorway so the bottom flight had to be shorter at only 6 stairs. When it came to final measuring before ordering I had a bit more wriggle room on going, so made the going as long as i could which made the angle of the stairs about 41 degrees, comfortably lower than the maximum 43 degrees.

Can you show a picture of your solar PV meter with as much of the visible wiring connected to it showing in the picture as possible, and a picture of your main incoming house meter and your house consumer unit. Then we might be able to piece together if it is wired correctly or not.

Loft roll is soft and will be unlikely to just stay in place. Frametherm is much stiffer and if cut slightly oversize will push in place on a sloping ceiling and just stay there. Early in the build I put a single piece in the roof between the rafters as a test , and 6 months later it had not fallen out or even slipped.

Well done. I bet the challenge was getting oak planks for the half landing that matched the stair, or did stairbox supply those?

Very similar to @joe90 stairs Shown here as work in progress. The 2 flights of stairs were 2 separate stairs from stairbox and the half landing was framed in place. Two 8 by 2's spanning the width and 4 by 2's spanning front to back. P5 chipboard floor. Where it gets tricky is if you want e.g. an oak staircase without stair carpet, then you probably do need to get the whole lot made by the stair supplier.

Scottish regs do indeed require a CO2 sensor in the main bedroom. I missed out on that as mine was built to the version of regs before that. I did look at buying one out of curiosity, but they were hard to find and expensive. with every new house in Scotland needing one, I would have hoped they would be easier to find and cheaper now.

At this time of year, solar PV output is very close to minimum,nothing like what they generate in the summer.

Air to air heat pump aka air conditioning unit, you get about 4 times as many kW of heat as it consumes kW of electricity. You can buy one for under £1000 and they are (just) possible to DIY install. Unless your whole house is using storage heaters, I question of the night rate saving is worth it as the day rate will be higher than normal.

Look at caravan and boat layouts, they have mastered small and awkward spaces and multi function uses. But don't assume many of the tricks in caravans and boats will meet building regulations if that is an issue to you.

The fact you CAN does not always mean you WILL.

100A single phase is 23KVA 100A 3 phase is 69KVA So they are pretty much saying you can have a normal 100A supply either single or 3 phase. You won't need anything like that, so no need for a new transformer, which is good. Probably worth getting 3 phase if available as it won't cost much more and you don't have to use all 3 if you have no need.

Christ on a bike.

Mine routinely turns on and off twice per second (not as fast as @Radian system) It's called "burst firing" meaning the on time is adjusted in this case to match available power. And Burst firing is used for industrial heater power control e.g in a furnace. You would have thought if such burst firing was detrimental to the life of a heating element, it would be well documented?

What do the heat loss calculations actually say your heat input requirement is? If the (much less than) 70W heat loss from the cylinder is going to overheat your house, then you better not let any people into the house (300W per person) and most certainly don't let them do any cooking.

Few self builders would cheat themselves would they? It is the mass house builders that are often suspected of only building a few properly, the sample that needs inspecting by BC, and cutting corners on the rest where they hope nobody will notice.

I would be having kittens if I was paying £23 per day even with a heat pump.

I have not looked but can you get that for only the free channels without paying any subscriptions?

Post a picture of the roof for suggestions. And it DOES need notifying to the DNO if grid tied. Gluing them to the roof seems a bad idea it anything goes wrong with a panel or if the roof needs maintenance.

I looked into this for a friend who is not allowed an outside tv aerial (conservation area) and cannot get a decent signal with an indoor aerial. Her only option is to stream her tv over the internet and that means a different app for each provider and of course the app won't allow you to skip the adverts (I prefer to record such programs on the satellite PVR and fast forward the adverts)

You will need one more 32A mcb as you presently have 6 30A fuses and that Cu conly comes with 5 32A mcb's.

I have fitted many of the SF BG boards, nothing to complain about My favourite if money no object is Hager (what i have in my house)

No. Any mcb's you find for that will be old / second hand, if you do find any new ones they will silly money. And an rcbo for that is like hens teeth. Spend the money on a new up to date consumer unit.

Which is original house footprint and which is a previous extension?

I think the SAP report is as good as the assessor and what you instruct him to do. Ours was pretty detailed and used the actual calculated U values for the floor wall and roof make up, and reasonable assumptions about windows and a random choice of ASHP and MVHR units. and a pretty poor assumption of air tightness. At completion time I got them to update it to include actual as fitted window UW values, correct a mistake that got the roof U value too poor, include the actual ASHP, MVHR and stove used, and include the actual air tightness test result. This improved the score somewhat.