ProDave

Draw it on paper. It makes no difference. You either set the rafters high and insulate below them, or set them lower and insulate above them. The thickness from plasterboard inside to surface of tiles on the outside is the same. If you want minimum thickness, which it sounds like you do, then a hybrid roof, some insulation above the rafters and full fill insulation between the rafters. That is actually what we have. It just needs a little more design.

Pause right there. For room in roof, I 100% recommend a warm roof construction (insulation above rafters) and air tightness layer following the roof line of the whole house, so even the eaves space that may not be part of the rooms upstairs is air tight and warm. This is SO much easier to detail and get right and so much better without lots of cold parts of loft to be separated from the warm rooms. This also then makes it easy and desirable to separate the function of floor joists and roof structure. We have posi joists for the floor upstairs and then a cut roof hung from a big ridge beam. So not only is all the roof space insulated and air tight, there are no joist members intruding, so you have a completely open loft area to do as you like in terms of what is accommodation and what is storage and how they work together.

I checked that and was told that was only if unfenced. If your boundary is the highway and you have a fence on your boundary, that does not apply. So I erected a fence, did my work on my side of the fence right next to the boundary and then took the fence down.

What could possibly go wrong?

This is why my advice at design stage is build a house with a warm roof and all insulation and air tightness following the roof line. Lovely warm loft and no bother with lots and lots of detailed air tightness at the junction between a warm room ceiling and a cold loft above it.

The air being expelled will contain moisture, and will have been cooled somewhat by the heat exchanger, but it is still likely to be warmer than the air in the loft. so unless the pipe runs in the loft are impecably and well insulated there is scope for the moisture in the air in them to condense. Mine is all contained within a warm space. I get the opposite problem, in spite of being insulated, in very cold weather, the incoming air is very cold and occasionally I get condensation on the outside of the supply pipe passing through the warm space.

I would question if the flow rates are adequate or is the MVHR unit in a cold place like a loft? Only 5 years uses but ours is still looking clean.

I had similar with car insurance. When I built the garage at our house I declared to my insurance on renewal the car was parked in a garage. THEN they told me the reduction in the premium was £0. I then asked what if one night I left it on the drive and it was nicked. Sorry not covered. Needless to say it is declared to the insurance now as stored on the driveway overnight. Madness.

This is not "advice" but mine (different make design) came to a dead stop against a flimsy plastic pip and maxed out at barely 60 degrees. Turning it a "little" harder the pip broke off. I then turned it further a little each day noting now hot the cylinder got before it cut off. I stopped at 75 degrees. If you try anything similar, entirely at your own decision and risk.

The quality of work is going down hill.

I think the more important question might be what is above the ceiling? What is making that one of a set of identical lamp holders get hotter than the rest? Is something blocking the ventilation holes? Is there insulation there? Is there a hot pipe running through that section of ceiling meaning it is a much warmer space? etc etc.

Post some pictures including the areas of concern.

Like when I energise a new electrical install I say "time for the smoke test"

I used flexible I think it was 70mm twin wall. If it is bought as conduit, the inner wall is a lot smoother than the outer corrugated wall, and it comes with a draw cord installed already, but that is usually just a bit of fishing line, so first use that to draw a decent bit of rope through before burying it.

I would go for outline planning, that is what most buyers of a plot would expect. You can include as much or as little detail as you want, but the drawings can be a lot less detailed than full planning so quite possible to DIY if you want to. From the fees point of view a normal planning application looks far better value than any pre app advice which we know from this forum is likely to be inaccurate an non binding any way, i.e. a waste of time and money.

There is your answer. the conduit is probably crushed by a stone somewhere and sadly useless. For anyone reading, only use a much larger smooth sided rigid conduit. 50mm absolute minimum.

Henley blocks and your bank of switch fuses need to be withing 3 metres of the suppliers meter. Simple.

Often the first sign of trouble?

Leave them alone. Some future electrician will thank you when he can thread a cable through the existing hole rather than drill a new one.

A "Bulb" is something you plant in earth and it grows into a plant.

Don't fit UFH in this situation. Your overlay boards will not have anything like enough insulation to sit directly on an uninsulated floor. If you do proceed expect a lot of your heat to go down and very poor performance.

Put all your "plant" stuff along the back wall of the garage, and I bet you will still fit 2 cars in there.

What restricts you to 40mm? What is the bottom of that 40mm? 25mm battens UFH pipes between pug mix and 20mm engineered wooden floor is what we have, only 5mm "too thick" for you. What insulation and floor build up below your 40mm starting point?

And unless the run to the sub boards is long, once fused down 16mm is plenty.

I would go straight from meter to henley blocks then feed each SWA with a switch fuse.