JohnMo

Why - you are laying for the system to be installed so it will come with MCS certificate, which means you get paid for export, so why not sell the electric. DHW heating is fine if you don't get paid for export. Gas or heat pump DHW heating is around 6p per kWh, export around 15p on the correct tariff. I would look at a system that doesn't demand internet connection - GivEnergy does require internet, others no idea.

Why - I'm over 60 and was taught metric at school, it's been taught in school since about 1965! Only time since leaving I used imperial was working with equipment designed in 1940s. And ordering wood in imperial cross section (which it isn't actually that size - 147mm is actually 5.79" not 6") and metric length - but building industry is backwards in its thinking anyway, so cannot expect much different really.

Your boiler is a weather compensation boiler, so why not use it as one? Does your system follow the rules in the manual Note. Systems incorporating zone valves which could completely cut off the flow through the system must also include a bypass. The boiler does not normally need a bypass but at least some radiators on the heating circuit, of load of at least 10% of the minimum boiler output, must be provided with twin lockshield valves so that this minimum heating load is always available. Balancing 1. Set the programmer to ON. Close the manual or thermostatic valves on all radiators, leaving the twin lockshield valves (on the radiators referred to above) in the OPEN position. Turn up the room thermostat and adjust the lockshield valve to give an uninterrupted flow through the radiator.These valves should now be left as set. 2. Open all manual or thermostatic radiator valves and adjust the lockshield valves on the remaining radiators, to give around 20oC temperature drop at each radiator. 3. Adjust the room thermostat and programmer to NORMAL settings.

Well done you.

You may have an issue with the UFH manifold return leg collecting air? You will need a method to bleed the lower manifold and the piping run going to it. Also the return line you need an expansion vessel and safety group, something like this, after the filter isolation valves https://www.unventedcomponentseurope.com/expansion-vessel-25-litre-heating-fixing-t-bar-system-kit.html/?utm_source=Google Shopping&utm_campaign=Copy Unvented Components Europe&utm_medium=cpc&utm_term=879559&gad_source=1&gad_campaignid=17178278874&gbraid=0AAAAADCTOYDo74Yo9HePQuEMKnbFqfg6s&gclid=CjwKCAiA86_JBhAIEiwA4i9JuybXCf4Z5_Ln7s1jNmeqsPnHSW3goCc-0aIt_EChTwzn0-N3iEqenxoC5xkQAvD_BwE

Can't you get a filter in the vertical on the return after the tee? Then you only need one filter/strainer. I would redo the tee before you go through the wall, to make space. Rotate tee horizontal, add filter, then loop up and out off wall or something like that. Your pipe is huge so no issue with pressure drops feeding 3 loops

Yep. You certainly have nothing to complain about if you don't vote, you are obviously happy with everything, anyone throws at you.

So basically all the gaps you see need to be filled. I would look to use a good expanding foam. Some of the vertical filler pieces of PIR, don't look to butt up against the OSB roof cover. All PIR needs to be hard up against that.

It's is actually buried in here

There was a thread on this the other day

Are you sure, you should have CO for carbon monoxide - not CO2 for carbon dioxide. We breath out CO2, cars, boilers and gas hobs put out CO.

Been there done that - used solar predictions to match charge with expected solar generation. Worked sometimes the days it didn't made the whole exercise a waste of time. Have data only in home assistant where it doesn't matter. Now just charge to fixed points 365 days easy no thought, and excess PV gets exported anyway. You really don't want anything that demands internet access to retain functionality. I would also look at Sunsynk.

Your system will have either a valve like this, this is to prevent pump dead heading Or you will have a radiator always open - bathroom or hall?

Think we may need a sketch

I would have it inside. I removed mine, pressure drop was huge. Installed a proper full flow filter. You can alway install something on each leg as it splits.