JFDIY

Logo is Roto, Seems to have been updated and the company become hyphenated. https://www.roto-frank.com/en/ It's worth trying them, sometimes it's surprising how keen they can be to sort you out. Also search for an old hatch on gumtree, eBay etc. Where you can get the bit you need If you have the broken bit it could be welded back together.

Surely as a last resort ,a retrospective planning application would tidy this up, almost laughable that it's been there 12yrs now it's a problem, do your repairs take it significantly away from the previous structure?

Don't think they are, I've got a KQ board in my garage and should you be brave enough you can live swap breakers in and out. The easy 9 doesn't have the extra lugs/contacts to allow this

Yes, Just get the power provider to install a three phase meter to a cut-out isolator, your electrician can then run normal 'tails' from one phase, neutral and earth into a standard single phase consumer unit to get you running for now. Careful trying to mix phases in the dwelling, you really need something like 6ft separation if memory serves, so putting your appliances across more than one phase in a kitchen could be tricky. I believe the reason for the separation is do that you can't get a 415v shock, but that either needs two concurrent faults, or someone meddling who shouldn't be.

Stickatak super blue worked for us, think it's rapid set so the fitters did one room at a time, and by the time they'd had a brew the carpet could be fitted to the first room. I'd go into the shop supplying the carpets and ask them to supply it, they may offer to do it for you and include it in the price, just tell them you've got underfloor heating and chances are they won't want the liability of puncturing a pipe. If you hot melt glue gun them then cut them into shorter lengths around 8". To 1ft, this means the glue will still be hot when fitted to the floor and you can apply decent pressure to it while the glue takes hold. This is how they did one of my folkes' rentals

To make it look nice, cut out all the broken stuff first so it's an equal and even gap, otherwise when the new caulk dries it'll shrink and still show the original stepped stuff through

Which way is pump arrow, should be upwards. The reason the manifolds need to be swapped is that the flow regulators only really allow correct flow in one direction, yours are being blown shut by water passing through them in the wrong direction, probably limiting flow. Is your extension off the same manifold, or a different one?

Lay the pipe with the twist the other way, then the push down at ends and rise less severely in the middle, when filled with water should flatten out better that way.

Mixer looks to be in wrong way round or manifolds mixed up. Check supply and return from boiler are correct first, If so easiest fix is to swap upper and lower manifolds over, check pump casting for flow direction arrow as mentioned by Peter. You might need to turn the image below upside down to match yours, but you'll see what I mean. https://www.colglo.co.uk/file.php?filename=UFCHF5530%2F970035.pdf

I think the difference is keeping electric cable and copper pipe seperate. Elec cable is purer and worth more than copper pipe, unless you burn the insulation off. I always strip mine

Can you build on a raft and sidestep some of the foundations bluff

What about the individual units that can be fitted in each room with just a hole cored through the wall. Can't remember the detail, but there are someone that will wirelessly talk to each other, presumably can be configured as supply or extract as required. There are also some room only units which inhale and exhale through a heat exchanger so change the air in the room where fitted more than the whole house as it were

Or have them activated from light switches. You either need double pole switches or my plan of using a UFH wiring center with relays to have the light switches as the input and the boiler run output to the MVHR boost. If you don't separate the switch inputs the turning in the lights in one bathroom will put them on in other linked rooms. Then of course a PIR sensor in each room would work too. In practice if the MVHR unit has a humidity sensor in it you may will find you don't need the extra inputs, mine seems to work quite well by itself in this respect so far.

Wouldn't s new pump in the old boiler be a much cheaper option? My sister's boiler packed up in Feb, pump failed, plumber got a new pump (or so he thought) the next day, when he removed the old pump it was all sludged up. The new pump was incorrect so he cleaned the old one up and refitted it, no issues since.

If the chrome arm will stand a lot of thread inside it, I'd be tempted to cut a 3mm or so wide slit across the end face about 4-5mm deep so you can wind it in with the side of an angle grinder spanner. Your double nut idea will do the same, if you haven't got a spare nut, for 1/2"BSP the nuts of most 15mm compression joints will go on the end.

Do you need the internal hex? If not a 'running nipple' is basically threaded tube, upto around 4" long, which you could cut down if needed I'm assuming that is 1/2" BSP thread like a backplate fitting (on the wall) would take?

Are you having any fabricated steel in other parts of the build? If so, you could have a piece of plate (20mm?) welded to the underside of the steel beam at the bearing points to raise it up to match the block height. In your drawing you show no mortar under the blocks to the steel, wouldn't they normally be on a mortar bed?, this will take 10mm.

Get a few scaffolders to quote, most will do a deal, we found the standard is 12weeks hire, overruns can cost 10% unless you strike a deal upfront.

Friend of mine is a plumber, he lived in a house with ASHP, that he fitted, with no issues for 5years. Rented it out and after several years and different Tennant's took it out and replaced it with a gas boiler. Rental market don't want to pay for something not running when the property isn't occupied. Either choose your Tennant wisely, have a backup plan with perhaps instant or localised heat. Or put the ASHP on your own KWH meter and rent it out with the heating included and you re-imburse the Tennant somehow to cover their cost in the elec bill quarterly or so?

Don't let @Onoff know, it's only 6⁰ in his bathroom, bet Mrs onoff is well impressed

@ToughButterCup not sure if you need the info now or not, here is a pic of the stand-offs and bobbins my towel radiator uses for mounts. Bobbins go on wall, standoffs on rad, grub screw through the side of standoff holds it in place

They're 250v so just put a plug on them and power from an extension lead, simulate them coming on and off a few times through the day as required?

Expansion vessel? My sister's was ok in summer when the heating wasn't really used (she's super tight and thinks a 14⁰ house is acceptable. Come winter it would need topping up every couple of weeks. The tell tale was when cold, the system pressure was about 0.75 bar but used to go to about 2 bar maybe more when running the heating. I witnessed it spilling water from overflow on one occasion. A new relief valve and expansion vessel and I haven't been called back.

I'd be concerned. I hate to scaremonger, but you need to start talking to the land owner, I've heard of cases where an over hanging guttering has resulted in people loosing their entire house due to legal parasites and stubborn neighbours. If he wants £10k, snap his hand off, more likely it's worth £50k+ to get a amicable resolution of things maybe more. What is the house worth with that side of the house blocked off and being a semi-detached to a farmer's shed? I know I'm painting a bleak picture, but expect the worst and hope for the best outcome Good luck

Would that be driven by the ceiling requirements of where the valve is to be fitter?, i.e. if your building regs quote 'XXmins of fire resistance' or similar then the valves must maintain that same requirement as the ceiling