Temp

I think B&B would work well but might be a bit more complicated. You would probably need to build walls for each end of the beams to rest on. The wall near the house could be just blocks. The one furthest from the house probably brick and block or block clad with timber. Once done any paving or tiling on top would be pretty bomb proof.

I don't think our BCO looked at it. I think in theory we have about 3" of fall over about two meters of pipe but because the flexi lays on the floor most of the run is flat. Hasn't been a problem.

I don't think PP is needed in the garden provided some rules are met.. https://www.planningportal.co.uk/permission/common-projects/solar-panels/planning-permission-stand-alone-solar-equipment-panels-not-on-a-building-but-within-the-grounds-of-a-house-or-a-block-of-flats But in a field its a different matter. Pretty sure a full application would be required.

I sympathise. The planners speant a year telling me the house had to be right at the front of the plot where its too narrow. Then we found a letter in which they told the previous owner that a house "further back might be better". You can try and point out the inconsistency to the planners but if that doesn't help you can point out the favourable opinion and improvements at appeal.

We have a free standing bath. The waste pipe comes out of the wall at floor level. We used flexible pipe to connect to the trap on the underside of the bath. We actually used more flexible pipe than necessary so the whole bath can be moved away from the wall for cleaning. Our taps are wall mounted.

I'd compact the ground and the MOT in two layers.

Sorry I don't have any info on the tester. I assume the coating is metal based so it's slightly conductive. It should be on the indoor side. Some of our windows have a dozen small panes/lights and the BCO tested every one of them. If one didn't pass he opened the window and tested the outside. That's how we knew a few were in the wrong way around.

I can't think of a reason why that wouldn't work. Some drawings show the strap on top of the rafters and fixed to the brickwork not "built in". Perhaps use a strap with a longer vertical section so the fixings are lower down the wall?

Low battery is usually a single chirp or beep every 15-30 seconds. Alarm is full blown, you ain't sleeping through this, continuously sounding and loud. If its a low battery they usually take PP9 / 9V batteries or they have a 10 year battery that you can't replace. If its the latter Screwfix or Toolstation will normally have suitable replacement. If its a real alarm I'd turn off anything that has a flame (boiler, gas oven/ hob, gas fire, candles etc) and I'd get a Gas Safe Registered Engineer (used to be called Corgi) to look at it. If there is more than one possible source perhaps ask the Tennant which they were using when it went off.

When it starts modulating down prematurely what actually happens to the the flow and return temperature? Think the return temperature should give clues.

How old is the system? When you say it's always done it do you mean since built it or since you bought the house? My first thought is the system has a slot of sludge in it. Possibly no or not enough corrosion inhibitor? This could explain both the "air" and inconsistent flow. If that's a possibility I'd look at draining and refilling the system, turning it on to stir it up and repeat until the water is reasonably clear. Then dose it with the right amount of Fernox F1 or similar. Read the instructions. It's likely to need several bottles. Helps if you can measure the volume of water when you drained out earlier. Putting too much inhibitor in doesn't usually hurt. You can also get test kits to check the concentration. Other possibilities could be an intermittent of failing pump? Undersize or faulty expansion vessel normally caused water out of the PRV.

We had an IBC on our allotment, it had a metal frame but I doubt I could be buried. The plastic part was more flexible than a watering can.

You could ask an estate agent what they think it adds to the value of your house. Although they will probably charge a fee. Don't invite the neighbour to attend when they visit!

Here's a really long shot... has the bathroom light been replaced with an LED bulb? Sometimes LED glow faintly when off due to capacitive coupling between live and switched live. I wonder if this capacitive coupling is enough to fool the mvhr into thinking the bathroom light is always on so its alway in boost mode? Probably not, but if you have an old filament bulb might be worth trying just in case.

What tends to happen with mvhr is the bearings eventually fail but they can sometimes be replaced cheaply yourself if you are mechanically minded. However my guess is its working and stuck in boost mode or just set too high. Presumably there is no obvious humidity sensor? Sometimes they are in a duct. Perhaps ask a few neighbours if they have any experience with the units or who they use to fix them?