ProDave

Note the direction of rotation of the NEW fan. Then temporarily re connect the OLD (you don't need to mount it in the unit) and note it's direction of rotation. I bet they are opposite. Do that test and let us know. Also, take a photo of the PCB from the other end so we can see the writing on the board next to the fan connectors.

No problem. An mvhr input vent at the dining end of the room, and am mvhr extract vent at the cooking end. Recirculating cooker hood with carbon filters will take care of most of the smells.

Re gas consumption. Simple laws of physics, if the boiler is burning and heating water it must be going somewhere. If the house is only just reaching your target temperature, then it won't be wasting massive amounts of gas. There are probably some savings to be had by optimising temperatures and improving efficiency, but probably not massive savings. What it the context here? Old house? New house, have you just bought it and this was what the previous owner had etc etc. Frankly bottled gas would be my last choice for heating, an oil boiler would have been a better bet perhaps?

What is an "upper villa"? A flat or maisonette? General pictures of building and which bit is yours?

Can you post a picture of the UFH manifolds including close ups of any valves dials or controls? Is this bottled gas as you are using the unusual measure of Kg of gas used?

I don't have time to be "nice" with them, they are rodents, pest and cause damage. Find a length of old drain pipe, lay it along the ground behind the ASHP and put a tray of rat poison in the middle of the drain pipe (the pipe is to stop larger animals getting at it)

I have just found the UK wide site to search this new UPRN database https://www.findmyaddress.co.uk/search

I was looking at something altogether cheaper than that. Like PV itself, it needs to be cheap to be viable.

I have often thought about such a system, but it won't be off the peg parts and it won't be a job for an electrician, more a job for an electronics boffin. In my case I have a home made PV dump controller based on an Arduino. so I would add to that to turn on a charger when there is surplus to charge the batteries. The same Arduino might as well turn on a grid tie inverter to discharge the batteries when import is detected. The only bit of that I had not solved was an off the shelf grid tie inverter that lets you set the output power. It is the cost of batteries that has stopped me experimenting with this.

You can build a small single storey building under the "caravan" regulations. To legally be a caravan it does not need to be on wheels but needs to me moveable in some way that can include picking it up with a crane and lifting it onto a low loader. Such a building is exempt from building control except for any drainage system that it is connected to. It might still need planning permission, that is separate.

I assume you are talking about render on the outside not plaster? This is surprisingly common around here to see this done but I wonder how it works properly. The bottom of it is below the DPC and so will be prone to getting tamp from the ground and bridging the DPC. I had exactly this on a previous 1930;s house. The walls had "rising damp" in several places, completely cured by removing the lower render and terminating it with a bell cast just above the DPC and leaving the lower brick exposed. So I do wonder what troubles are being stored up for the future if you do take the render all the way to the ground.

The big one for me is mice can chew through them. Ask my neighbour who had 2 leaks and 3 bits of ceiling down before he caught the mouse. Of course make your house air tight and mice won't get in. And the previous static caravan, could not stand our high water pressure and a lot of the plastic push fit fittings started bursting.

1: A monoblock ASHP puts the noise making bit outside. For some strange reason this bothers some people but I would rather have it outside than in. 2: GLUE and SCREW the F out of your floor boards and they won't squeak or creak. 3: Pipes need to be free to expand and contract. What you describe is usually where pipes are in a slot under the floor and are tight, so they can't just expand quietly, the expand a bit, winding up like a spring then go "click" as there is enough force to nudge them along a bit.

Yes. Move in. If the builder grumps, tell him the alternative is you might go bankrupt and HE might not get paid. This is the best solution for everybody including him.

Fit a proper air tight membrane over the inside of the rafters with all joints taped, and taped to the air tight layer on the walls.