ProDave

I did. My 40mm gap at the bottom is with ceilings first.

Hi and welcome. A plot at auction without PP is probably for auction without PP because it stands little chance of getting PP. Be very wary of that one. When the hammer falls, you have bought it. I would say don't design the house until you have the plot, so much depends on the size, shape, orientation, views etc. But do start thinking about what you want in a house, and what sort of construction method etc.

Re MVHR, you really need to spend some time in a house with it. The air in our house is always fresh. Never felt the need to open a window to "get fresh air" and kitchen smells don't linger and don't spread to other rooms, the mvhr extract vent not far from the hob deals with all of that. Contrary to what many think, it does not recirculate air around the house, it extracts stale air and injects fresh air, exchanging heat from one to the other in the process.

Probably but I would need to practice, the levers work "wrong" compared to a 360 digger.

I am the opposite to @Onoff We have a floor to ceiling height of about 2440mm. I just love the fact i have been able to board all the walls without cutting a silly little bit off the end of each board. The 40mm gap at the bottom will be covered by the skirting.

use a web browser Freeview EPG https://www.freeview.co.uk/tv-guide#rOc0dk2JgcqBExzp.97 Freesat EPG https://www.freesat.co.uk/tv-guide/

Is the bottom layer foil backed by any chance? I guess it's time to have a look through all the downlight holes to see if you can see anything.

The floor tile thing. Due to complete ignorance, at the last house, I stuck floor tiles direct to ordinary P5 chipboard with UFH. 15 years later they are all still intact, no cracking, no loose tiles, no hollow sounding tiles, not even a crack in the grout lines. Topps tiles must have saved the day by selling us a "flexible" tile adhesive that made them work when everyone says they should not.

I am guessing that the joists run the "wrong way" and looking from the downlight hole to the drip mark, crosses one or more joists so you can't see that part?

I don't know why you are having the issues you are. I know mine is a different make and design of house, but it shares many of the well insulated, air tight, low energy credentials. I have been very satisfied with the performance. I particularly like how it maintains such a constant temperature. Nothing happens quickly, it won't cool down quickly and it won't heat up quickly. Maintain the correct low level heat input and it maintains a comfortable temperature 24/7 regardless of what it is doing outside. And the controls for that are nothing more than 3 room thermostats controlling the 3 UFH zones downstairs and a conventional central heating time clock (mainly so I can have the heating off at night for a totally silent house). My house has also proved that in a well insulated house, even in the Highlands, you don't need heating upstairs. A "control system" that is over shooting and under shooting (too hot or too cold) probably has too much "gain" which in this case means too much heat input. Or at best it is not tuned correctly. A lot of my professional life was control systems and I have seen plenty that are unstable. The trouble is the average "heating engineer" probably know sod all about real control system theory. Lots of things will interact so you need to sort them one at a time. Get the MVHR balanced first. If it is still under and over shooting, the problem is the UFH. You want that to be producing gentle heat at just the right rate, not bursts of too much heat (which will overshoot) then by the time it eventually cools down, it will take time to heat the slab again from cold, and while it waits for that it will undershoot.

If I can buy the last velux windows, the stuff for the en-suite bathroom and last of the stuff to fit out the house we will be about there. Then it is just that sun room, and loads of outside stuff like decking, steps, ramps, landscaping etc. In the mean time the ethos seems to be a reasonably constant run of stuff purchased so nobody can claim we stopped buying stuff so "must have finished"

We have an acrylic bath not too disimilar to that. I must admit to being a fan of pressed steel and enameled baths, but they seem quite rare now. Would not want cast iron again (unless you like sitting down and getting a cold bottom)

This VAT reclaim deadline is starting to worry me. I think for us it is handy the council tax man has delayed valuing the house until the summer at least, so that has bought me a bit of space during which we are still living in the caravan (cough). But I am planning to get a temporary habitation late in the summer and do the VAT claim then. There will still be some things left to do which I might miss out on the vat for, but some big items like the windows for the sun room I can still get VAT free as I will be getting them "supply and fit" and it won't be completed then so it still perfectly valid for a new build.

Cutting a trap in a ceiling and then patching up with a new bit of plasterboard and skim or tape and fill would be a lot easier than lifting tiles upstairs. Cut a small hole to start with to see how the joists run. Ideally then cut the trap back to the centre of two adjacent joists once you can see what is where.

Rainfall shower head in the ceiling emptying direct into the WC bowl. Rinse your hands under that.

I bet that is a "value engineered" plastic part that has snapped. Reminds me of a well know make of bathroom fan heater where the pull cord operates on a simple see saw lever that pushes up on a switch when you pull the cord down. It is a grossly under engineered bit of plastic. The one in our static caravan snapped. It took me about 5 minutes to make a replacement out of a bit of steel sheet with a hacksaw and a file. Not pretty but a LOT stronger than the inadequate original. The strange thing is, I have replaced several of these heaters with a new identical one with the same silly plastic lever. Why don't people learn? my reaction when something like that breaks is I would actively seek a different product rather than reward that manufacturer for using a defective part.

I probably didn't research the different options well enough at the time. It was the builders that built the shell that recommended I used Frametherm 35 instead of blown in wood fibre, which was the original plan, and I never questioned the 35

So the brief for the new controls engineer they appoint: Sort out the control system so it accepts charge properly. Undo the "value engineering" to replace failed parts with a different make, to make the product reliable. Spend a few pence per unit on bootlace ferrules. Add some basic status monitoring to the controller. Properly document all features like the location of an overheat resettable trip.

I have always wondered why nobody seems to market a nice looking set of hand rails / grab rails etc for a disabled bathroom. They all look so cheap and nasty, buts of bent tube with the ends just flattened for fixing screws etc. Surely someone must make some that actually look like they have been designed?

I have always regarded Finder as very much budget stuff, nowhere in the league of ABB, Telemech etc. Glad you have sorted it without pulling your plant room to bits. Next time (if there is a next time) do an ohms check on the outgoing pair with the contactor open.

I am in the minority here using a 30mm thick dry sand / cement "biscuit mix" for the heat dispersal medium in my suspended timber UFH. I am very pleased with the way it works, FAR better imho than spreader plates. We don't get overheating issues but as mentioned that is probably due to our location in the north, rather than any particular design genius.

Lets hope the new contactor fixes it. It seems odd for the contacts to have burned out so soon, it's not as it it is switching a demanding load and under load conditions.

This self build community is quite common up here, though on a smaller scale. The road we are in, has 12 houses. 9 of those are self builds, but done gradually over the last 20 years. Not many original owners still in them though, most tend to build a house, live in it for a few years and move on. 2 of the self builders built a house in the street then built another a few doors away (we are one of those 2)

It needs someone with a working one to probe it with a multimeter. some resistor colour bands can go odd colours if the resitor is routinely running hot.

= 10K ohm (10,000 ohms) If it has burnt out, it almost certainly means something else has gone. but worth a try. I would not be at all surprise if FET1 was dead.