ProDave

Just jack up both ends more, yes it will bend the chassis back to being more straight. Ideally you want all the supports to be taking their share of the weight. At the moment it sounds like the centre / axle jacks are taking most of the weight and the end ones are just stopping it tipping up when you all walk to the same end.

I have a different unit but the operation is similar, the bypass flap only diverts one of the flows away from the heat exchanger. But this brings the discussion to looking closely at that mechanism. If the bypass flap is not closing properly when not in bypass mode, it could perhaps be the route of the "leak"?

It probably came from a holiday site where they expect a relatively regular turnover of 'vans and they plug the mains into a socket like touring caravans do. Just ignore it for now. Most likely your electrician will connect the cable direct to the consumer unit in the 'van but he could also just fit a matching socket and just plug that plug into it.

I have an Enthalpy mvhr unit. It was more a case that one was available at the right time at the right price than any technical reason for choosing it. One advantage, not mentioned yet is an Enthalpy mvhr unit does not need a condensate drain, so installation is slightly easier.

Did they check the unit was actually connected correctly? When I installed my unit I found the terms used to describe the ports confusing. Could it be something like the supply vents supplying air to the rooms is mistakenly connected to the exhaust air port that should be exiting the house? I would have expected Brink to have checked this on their visit but perhaps they "assumed" it must be connected correctly?

That was an option I dismissed. It was a flat aluminium roof. Unlike tiles, there is nothing to slot that under. So it would rely entirely on being stuck down with some glue / sealant to keep the whole thing watertight. Any failure in that and it would leak. My swage up the under sized hole forms a natural upstand to divert rainwater around the hole, and I well sealed it as well. I guess I could have then put one of those over the top to make it look better.

Mine is a much more basic 'van with just a plain aluminium roof. Having failed to find any fitting or flashing made for the job I improvised. I cut a hole in the aluminium slightly smaller than the flue, then carefully swaged the edge of the hole upwards until the flue would just fit through. the swaged edge formed a small upstand so water running down the roof would run round it. The hole was cut mid way between the roof joists. In the void I fitted a clamp to retain the flue in place. There was glass wool insulation in the void that was cut back to clear the flue. The inner "ceiling" was hardboard / plywood material. I cut a larger hole in that to maintain the 50mm from the twin wall flue to combustible materials and covered it with a stainless steel closure plate. The kink in the flue as it exits my stove was to align the twin wall with the centre of the gap between joists. The stone the stove sits on and side and back pieces were all offcuts I had collected some time ago to put in the "that will be handy" pile, and they were. It was not possible to maintain correct side and rear "distance to combustibles" so I used stone slabs to protect the adjacent furniture and wall behind the stove, with an air gap left between the wall and the stone. It did a lot of burning and nothing got too hot or singed.

DIY

Yes wiring regs dictate you should not connect a caravan to a TNCS / PME earth system, they should be connected to a TT earth which in simple language means it's own earth rod. The black thing on the wire is a cover to protect the electrical connection clamp at the top of the earth rod.

I fitted a wood burning stove in ours. It hardly went out from November to February and kept us warm through a Highland winter at little cost but it was a lot of work keeping up with the wood to feed it.

Your stove flue should at least continue up into the ceramic flue above the slab and be sealed with a closure plate.

Build internal walls of timber and plasterboard. Then only supporting walls will need proper foundations.

Ditto to above. You want simple and reliable, then old fashioned hard wired light switches like we always had.

On mine the axle is just a tube between the 2 wheels and I lifted on that and put the first two supports under that. It was well balanced on the axle. It is not an officially marked jacking point but it is certainly strong enough. It won't tip up or move because you will have it hooked to your cars towball at that point won't you?

Here is what I did: some basic points. It will weigh something like 3 tons. So you need a good stable jack, I used a 2 ton trolley jack, much more stable than a bottle jack. They don't have brakes on the wheels, so nothing to stop them moving. To prevent mine having any notions of going anywhere while I was under it jacking, I kept the tow hitch attached to my Landrover. For support I used ordinary 100mm concrete blocks on their sides. You will also need plenty of small pieces of assorted thickness bits of wood for the final packing to get the heights right. Start by levelling the axle. Jack up one side and pack it with blocks then the other side. You need to get the axle level side to side as your starting point. I just used an ordinary spirit level on the floor of the 'van. These first supports only need to be high enough to just get both wheels off the ground. Once the axle is level and the wheels are off the ground it won't go anywhere so uncouple from your car that was acting as an anchor. Now use the jockey wheel to get the 'van level front to back. Then it is a case of blocking and levelling each jacking point. Starting with the ones at the extreme ends and then all the ones in between. I think I ended up with 12 piles of blocks and timber supporting mine.

All your plans show blocking direct access from the hall to the new kitchen. I would not want to have to go round through the living room all the time to get to the kitchen. If the "Sewage hole" (you probably mean inspection chamber) is in the conservatory then you probably have some drainage relocation and re routing to do before you can build a proper extension.

When buying my velux windows I was on a tight budget at the time and did a similar sum, and the energy saving on such small windows would never repay the extra cost in my lifetime so I chose doubles.

Turn ALL GF thermostats down. That should shut off all downstairs loops. And will also test my question, does the upstairs manifold continue to work and does the ASHP continue to work.

Then it should all work. Are you SURE it has been wired properly so when all downstairs rooms are up to temperature and the downstairs UFH controller is off, does the upstairs UFH continue to run and most important does the ASHP continue to run? Agreed some balancing needs doing, but apart from different rates of heating at the moment it should work.

You mention it "clicks off" at 23 degrees. Is this a room thermostat if so where, and is there a separate one upstairs and downstairs?

True, but that is probably a morning problem. Someone flushing a loo and the cistern re filling on a wall joined to yours can happen any time of the night, perhaps more than once in the night. so i would avoid at all costs a WC and it's cistern on an adjoining wall. If you can avoid a shower on an adjoining wall then do so, in this case the pipework and shower head (water flowing noise) could be on the external wall not the adjoining bedroom wall if you swap bath and shower positions.

Bedroom 4 and bathroom is not so much of an issue. The WC is shown on the wall adjoining the void and it is the WC flushing and re filling that is the biggest issue. So with that in mind, re think bed 4's en-suite layout so the WC is NOT hung on the wall adjoining Bed 3 The fact we are discussing such details shows the basic design is pretty good.

For some bedtime reading look at this thread Where he bought a large derelict stone house and has gradually rebuilt the stone outer structure and built a timber frame house inside it.

It should have been drained if not used over a winter. It it wasn't, your first job will be find and fix the leaks. (guess how I know that) Assuming it has been drained, as above connect the water, flush it through and good to go.

But that is 9 metres away and if the blockage is downstream you will need 30M of rods. I am sure BC wants rodding points closer than that?