ProDave

In a well insulated air tight house, you simply won't get that level of temperature change in such a short time. If you have heated the bedroom to 19C to get up, even with no heating in the depths of winter, don't expect it to drop more than a degree or 2 in 24 hours, so no way will you get down to 12C over night.

It would be interesting how much. I bought a good used static caravan for £4000 delivered, you can get even cheaper if you are not bothered if it is a bit tatty. No further bills regardless how long you live in it (council tax etc of course)

That sounds an expensive option? Most buy a used static caravan and then sell it at the end of the build (a few keep them after that) With an old static caravan that you own it is relatively easy to alter them to add things like washing machines, or set up another shed for laundry etc.

^^ Was he Australian?

Can you post a clearer picture showing the context and what are you concerned about? I am not understanding what I see there, some roofing,some pallets and some unidentifiable material?

What's the other side of the wall? Easier and less intrusive to cut a hole in the plasterboard to see and patch up afterwards. Any sockets on the other side of the wall, if so easy to spring a socket box out for a look.

Have you considered a knock down and rebuild? If only 3 of the original walls remain and not much else it would be better in so many ways, 0% VAT, start with a clean sheet on the design, if you are not having the garage and accommodating all parking in front, you could make the house wider and probably get the upstairs accommodation without raising the eaves height. Regardless of what you do, your drawings need to be clearer. you have a numpty of a planning officer that can't tell his left from his right, but either way, both neighbours have at least one roof window looking at your site. So your layout drawings should show both neighbours and the positions of their existing roof lights. Then adjust your layout so at worse it is a bathroom roof light with opaque glass facing your southern neighbours roof light and all bedroom roof lights do not overlook that existing roof light. Show it clearly on the drawings so there is no room for misunderstandings. e.g. none of us can tell for sure what roof light is actually looking straight into No 23 from those drawings.

Is this a knock down and rebuild, or an extension / renovation?

I used 25mm PVC conduit with swept bends. The ends are accessible under the island and under the consumer unit. I installed 10mm twin and earth. Way over kill for a couple of sockets but it can be used in future should we decide to change for an induction hob. If I really needed to I could pull something else through thanks to the swept bends.

Several people here including me took the "leap of faith" and only installed heating downstairs. And it is true, in a well insulated house with good air tightnes and MVHR, you don't need any heating upstairs. That will certainly cut down your install costs.

And most immersion heaters also have a safety cut out, usually in the form of a tiny almost invisible little red button that will pop out if it gets too hot, if that has tripped push it back in and it should go click.

Perhaps some pictures to put this into context, particularly if they also show these line posts?

It might be the immersion has failed, or take the cover off that box, there is a circuit breaker inside as well as the contactor. See if that has tripped?

That is unfortunate. It is a shame the neighbour did not notice earlier, very much earlier. It is not difficult to locate a party wall accurately, usually measurement from a door or window on the back wall that can then be measured on the outside. Have you (or the builder) done that to be sure it is over? If the builder has built the wall following the exact line of the party wall then the outer edge of the wall will be about 4" onto the neighbours land. If a party wall agreement applied then you would have either agreed to build the wall entirely on your land, in which case the aparent line of the wall would step inwards when viewed from inside your house, or you will have agreed to build it on the line of the party wall, in which case if your neighbour wanted to extend they could join onto that new wall. Agreed with above, this late knocking it down and rebuilding would be very expensive. First get the facts about exactly where the wall is built and by how much it is trespassing before discussing with the neighbour. They might just accept it is on the party wall line and they could join onto it if they wanted, it would be if the entire wall was over the boundary that things would get really messy. Was there no fence there marking the boundary before the extension was built?

And of course the big problem with safe zones, is nobody other than electricians knows about them, not even many other trades, so the protection they offer is minimal.

The proper reclaimed railway sleepers that really have seen previous use on the railways will have so much "stuff" impregnated in them, they will never rot. They would be my choice if you can get them. Cue someone else to come along and tell you how nasty all the stuff in them is and to avoid.

Except how do you plane the last few inches down to the floor? Chissel? Hand plane with a forward blade?

Mains cables to / from the CU must go straight up or down or straight left or right within the dimensions of the consumer unit (safe zones) As the Loxone box is wider, you could route data cables up / down the wall at the edges of the loxone cabinet to give some separation. Within those rules there is plenty of scope to get good separation, e.g. all mains cables to extreme right of CU safe zone and all data cables to extreme left of loxone cabinet.

But before then you just slopped "it" in the street. But @SteamyTea has put me off a crab sandwich, something I always like when I go somewhere making them.

I am more concerned with pictures 2 and 4, that looks like subsidence to me. If so the repair is much more serious and in the process of doing that the failed bricks could be replaced in sections like you do with underpinning. How old are the elderly owners? Is there a case for not actually doing much if it is likely to see them out without major work to spare them the worry and let the next owner down the line deal with it?

I would bet electrolytic capacitors, well worth trying a repair.

First question, what temperature is it heating the water to? (what did they set as the target temperature) 40kW is about what i use in a whole week for hot water in the deepest depths of winter when there is no solar PV to help it, and the incoming mains water temperature is very low. The legionairs cycle will almost certainly use the immersion heater. One possible problem is the immersion thermostat is set too low, and that cut out before it reached temperature. But agreed the energy would have gone somewhere.

It's a shame you didn't use Frametherm for the whole lot, this is much stiffer and does not sag. I did a test piece early on and left it 6 months with no support and it just did not sag.

Two paving slabs. The place it sits needed building up a bit, so a good place to uses up some rubbble , wacker it all down, sand, wacker that again, level it and lay the slabs. It's been there about 5 years no problem. The heat pump is slightly longer than the 2 slabs but at least the feet sit on the slabs okay.

I assume you know this but mention for the benefit of other readers, DC from the panels is lethal. At the very least leave each string of panels incomplete, i.e at least one dc plug and socket not connected so there is no potential on the cables while wiring the dc isolators and making the connection to the inverters.