ProDave

Probably 6BA then.

What do you call tiny? Old electrical boxes used to be BA threads, probably 4BA or you could tap it with the next size up metric tap. But BA size screws should be easy to buy.

What is the question? Looks like you have fitted the yoke into the back box and have a front plate / switch that will fix to that. What problem am I missing? Other than connecting to the remnants of the cable in the old back box (hope that is not 240V)

My wall mounted vents have a fine stainless steel mesh. They do a good job of stopping insects but they do clog up and need maintenance. You can't suck them out with a hoover as there is a louvre vent in front blocking a hoover getting close enough, so to clear them I take them off and blow through from the inside with the air line from my compressor.

HDD bearings are the one I marvel at. I know they are only supporting a small mass, but they can run for many many years / decades. So far my MVHR fan bearings are okay, but I had to replace the bearings on my ASHP fan at about 5 years old, so chances are I will be doing that every 5 years.

Go and buy something like this https://www.ebay.co.uk/itm/397148477114? That will enable you to test each individual leg of the circuit and identify where the fault is.

I still don't think we know if this heat pump is heating the house with radiators or under floor heating?

You can buy an old style, not calibrated insulation tester second hand on the likes of ebay for not much money that would solve this quickly if intent on doing it DIY.

But you are not going to find which one without an insulation tester. Unless you have the patience of a saint and try the "disconnect one and see if it still trips" method.

Yes, of course the tank will run out of hot water if not being re heated. If you must have 3 showers all in one go and can't change the time you shower, then I really think your simplest solution is change to a different tariff that does not have that hugely expensive period when you most need it.

As above, insulation resistance testing is needed Live to earth and neutral to earth. If you don't have one, buy one, or get an electrician. Clearly there is damp where the wet socket is. It sounds likely there is a lot of damp in the cable as well as just in the socket.

Best of luck with the planning. I fear it may be challenging. Lack of windows facing the view is probably because they had to work with what was there.

Same for me, but I got the impression it was a time delay, so walk slower and they cross closer to the target. But walking the other way and the target is half way between the two crossovers. I use 2 old bucket handles straightened out and then bent into an L shape. I didn't know I could do it until a discussion with my BIL over a pint of beer ended up "Here take these and walk across my yard" and they crossed over half way. "That's the drain pipe from the barn" he told me. I used it in anger when getting my water connection. The mains water was not where the plan given to the contractors showed. They were on the verge of packing up and going away, so I got my rods out and went walking. You could almost hear them sniggering, but the rods crossed over only 1 metre further than they had already dug to so they agreed to go a bit further and there was the water pipe.

Tip No 2. If you have a stud wall that is OSB boarded one side (for racking), BEFORE you fit the plasterboard, cut a hole in the OSB bigger than a socket box. Then cut the correct size hole in the plasterboard once fitted.

It's a personal thing but I like dry lining boxes. Buy the Appleby ones like the picture above, they are good and reliable. Some other makes with different methods of locating them can be dreadful. My top tip. Run socket cables horizontally around the room at socket height all the way round, with a bit of slack in the cable every now and then. Then in the future you can cut an extra hole in the plasterboard anywhere and add an extra socket, you know the one you forgot you might need.

Try it yourself first, I was surprised I can do it. Don't ask me how it works, but it does.

I am keen to see how this back to back WC into a single outlet works, and does it suffer the "swapped contents" problem?

I was visiting a relative recently, she had an extension several years ago with UFH in the extension. But the UFH "never worked properly" so after a couple of years, she had radiators fitted in those rooms and gave up with the UFH. I had no part in that discussion or decision. But following that visit it seems her boiler is set to heat "hot and hard" for 1 hour at a time. No wonder the UFH failed to do anything sensible.

A valid point to make here even stronger, is a Time Of Use tariff should only be used by someone who understands the different charges at different times of day (and with some tariffs they vary day to day) and then actively manages their energy use to consume as much as possible in the cheap times and as little as possible in the expensive times. If you don't do that and just "use it when convenient" I really don't think a time of use tariff is for you.

I don't know your particular heat pump, but there should be a way of setting a timer so it only heats hot water at certain times, and you want to set it so that it does NOT heat the hot water between 4PM and 7PM. Then you will just be using the hot water from the tank and it won't re heat it after use until the expensive period has ended. Same could apply to heating the house, set it so it does not do that between 4PM and 7PM. See if the house keeps warm with the heating off for those 3 hours, hopefully it will.

You don't need a servitude right for anything in your own garden. A servitude right gives you a right to do something on other people's land, like the example of my previous house where it allowed us to install a drainage field under the adjacent farmers field. That servitude right was presumably negotiated by the owner before he put our plot up for sale. Be very careful here, you have a system that might work now by discharging to somewhere unknown (I doubt that 2M pipe is enough) but you don't appear to have any right to do anything outside your own garden, IF that system ever fails, then you have no right to do anything on other land to fix it, or install any replacement system. Your own small garden will NOT be enough room. This is where you need a good solicitor that understands these things. He should be insisting the vendor gets busy and negotiates a servitude right with the owner of the adjoining field where this tail pipe leads to. I hope you have not yet concluded the missives?

With such a peak usage at the most expensive time, 4-7PM I suspect you might be better not on any form of Time Of Use tariff and just be on the standard fixed rate all day tariff. Time Of Use tariffs only make sense if you can use most of your energy in the cheap times and as little as possible in the expensive times. For most people with an all electric house it is impossible to avoid usage in that 4-7PM slot. P.S just "having a shower" in that peak time need not use any energy. The hot water comes from your hot water tank. Just adjust the timer for the water heating so the ASHP does not immediately start re heating the water until after the 7PM expensive period finishes.

Not in my house. Council tax is more than twice my total energy costs. But unlike energy costs I can't do anything to reduce it or swap suppliers for a better deal.

For the record I installed UFH in my first self build 23 years ago. There was no forum to discuss things with then, I was flying on my own. We installed UFH upstairs and down, each room on it's own thermostat and zone, driven from an oil boiler. No mains gas available and I had not heard of heat pumps. That system is still working. It has had normal maintenance, several motorised valve actuators replaced (WHY are they the most unreliable bit of a heating system) One pump replacement, and one thermal mixing valve replacement. And normal boiler servicing. What I learned from that is many (most) system designers are NOT experts. We were advised to have UFH pipes in the downstairs hall AND the upstairs landing. The hall rarely called for heat and the landing NEVER. That system should go on forever if you can get parts, when the mixer valve failed, it was hard to find a replacement, it is not a design of manifold that is for sale now.

Tail Pipe is the wrong thing to be asking about. It is the drainage field or infiltration field that matters. I don't literally mean a field, that term refers to an area of ground that has a network of perforated pipes set on stone buried under the field. In the case of out last house the deed of servitude indicated the position and size of that under the adjoining field. The good news is as long as it actually works, and it does drain somewhere, SEPA are exceedingly unlikely to ever bother you. In spite of what they might say, the reality is they are not taking any enforcement about people here with septic tanks discharging directly into the burn. But the bad news if you find it is not draining away then you will have problems sorting it out. Worst case is you have to dig up the field where your tail pipe leads to and re lay the drainage field. That will test if you really have a deed of servitude, so now is the time to properly get to the bottom of that. Make your solicitor earn his money. Do you have direct access to the watercourse or would you have to run a pipe over other peoples land to get there. It is worth exploring that so you have the option to upgrade to a treatment plant discharging to water. That is SO much better, P.S. the outflow from a septic tank will stink. The outflow from a properly functioning treatment plant should be a clear and odourless liquid.