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And if you try to insulate these pipes the cooling effect in the room would reduce which might be a negative... ... because I'd expect the heat sources to vary over the year. Winter will be the heating system, summer will be the solar electronics working flat out.

Sounds like a really successful build if this is the main worry after moving in! Not an expert but the little plant room that I have (boiler, cylinder, consumer unit with a few electrical bits) is similar, gets a lot hotter in summer. 27C isn't really going to worry electronics etc. I'd monitor over summer and if you find the room getting about 35C or causing other problems then may be worth doing something but 27C doesn't warrant much concern in my book.

I thought you had previously told us the flow temperature was set to 46. I'm not suggesting you change it. If it's something else tell us what it is. In reality the best flow temp is one that varies depending on the outside temperature. It's higher when its colder and lower when its warmer outside. But that's all to complicated to worry about right now. I'm trying to get you to focus on just the most important things. Everything else can be looked at in future.

@zoothorn Don't go changing settings you don't need to. 46 is fine. @marshian and I may debate what is best, but what you have is plenty to get your place warm. 46 is a perfectly normal temperature for someone with radiators. 'Medium' if you like. If it was over 50 it might be an issue. Long term lower may be better but it really doesn't matter right now when you are cold. Just focus on adjusting the timer. Maybe as a learning exercise set yourself the task of changing the evening heat period from 2 hours to 3 hours. Change nothing else. Just extend that time from 2 to 3 hours. Once you've done that we can talk about other changes. I've been busy today so will reply to the other stuff tomorrow.

A developer actually drilled through into the Northern City line near me (site is close to Old Street). They were piling foundations. Could have been very nasty.

I'd very strongly advise not touching it at all right now. Zoot has mentioned that this new system is the first time he has felt as if the system is working and outputting some warmth. Once the other issues we've talked about have been solved and the building is warm then we can talk about lowering this. But I think it's a really bad idea to lower it now before we have got the building warm. Zoot, in my view, you could increase the hot water temp to 55 rather than 46 if you want but don't touch the flow temp for the rads. Focus on figuring out how to adjust the timer and locating the thermostat in the right location.

Why not in the sitting room? What about at the bottom of the stairs? You can set up whatever periods you like in the timer. Lower temp at night higher temp during the day is about the simpliest way to do it. As we have said repeatedly, setting it that low overnight means your system will be overwhelmed by the cold. To maintain a comfortable temperature during the day you will need to maintain a higher temp at night. Having the temperature set a bit lower overnight is fine, but more than a few degrees will cause the heatpump too much work and the house will become too cold to heat. I know this sounds wrong to you and you don't like the idea, but all we are asking is you give it a go. We can work with you to find a solution for your bedroom so you can sleep comfortably, but the rest of the house should be kept relatively stable temperature (+/- 2-3 degrees).

But equally, your heatpump will produce more heat output per unit of energy input the lower the temperature. So if your set the output temp to 55C it might take 1kw input to produce 2.5kw output. But if you set the output temp to 35C it might take 0.5kw to produce 2.5kw output. So double the amount of heat for the same money. Zoot said his current flow temp is set at 46C. That sounds fine for now to me. I would leave that as is. The aim is to set it as low as possible while still outputting enough heat to be warm. Right now there are other issues stopping zoot from warming up.

Brexit hasn't helped either. A lot of the high paying finance jobs have dispersed and the young Europeans who used to flood london also.

If you do this the advice I've seen which seems like a good idea is to put the sensor inside a pipe/conduit with the end sealed to stop concrete getting in. That way if something goes wrong with the sensor you can pull it out and push in a new one. Can use either an extra length of PEX or flexible electrical conduit. PEX might be the better option as long as your sensor fits inside.

Thinking about this some more, I'm not sure this is a good idea. Zoot had this convo with Octopus a while ago. We are still in Winter and bills lag, so the surplus may be lower now. Zoot also has a new heatpump with a different setup and at this point it's unclear if it's drawing more or less energy. So leaving the Octopus surplus there gives a bit of buffer against surprises. As @sharpener has said this may be a little tricker on this model heatpump and there are some advantages to using the Valliant controller. So if what Zoot has can be made to work then it's worth trying that first. But if that is too difficult for whatever reason then switching makes sense.

Not entirely sure I get you. When I've thought through sequencing on this, to get this style I think you need to install the custom door frames in before plasterboard (definitely before skimming). This would the require protecting these frames so if I did that I'd build temporary protection frames around those frames. Those frames in turn should provide a standoff from the metal trim and therefore protection. Still, a lot of work. Edit: Read your post again, clearly you said corner beads and I was thinking about beads around doorways. Still a little confused as the bulk of the corner beads is the same as a normal wall. Guess you are talking that the area where the bead is mitred into the shadowgap beads at the bottom? If so, seems like an easy way to avoid that problem is to put some temporary rough skirting in the corners to avoid bumps?

The other option with porcelain/ceramic tile is to have mitred edges with a sliver of face tile on top resin bound. Load of extra labour in it though.

My slightly more nuanced take: It's an interesting idea that I have considered. Not for GSHP though as I suspect it's not a big enough area for that. My thought was to use the water direct for either cooling in summer (would also warm/recharge the soil for winter) or as pre-warmer for MHVR in winter. With no heatpump in the loop freezing would be a low probability. In a PassiveHaus class building then maybe a tiny water to water heatpump would be possible to top up heat but wasn't where my thoughts were leading and I think all the GSHPs available are way too big. Main concern was if it would cause problems with drying out under the slab and potential movement/insurance issues and I think for this reason it's worth ruling out even if the maths add up. (Not that I did the maths)

Haha, wondered if you'd say something like this. You can have fun or efficient not both