Are normal cylinders a lot cheaper than heat pump ones? Are they "vented" or "unvented" or doesn't this change with direct heating? Can an immersion heater recharge the water temperature as quick as a heat pump? Why would heat pump cylinder stop you heating it in cheap period?
Do you have to have regs or a warrant for that? What's the total size 6m wide by how long? What size timbers did you use?
Im thinking of extending a garage from 5m wide to 6m and it's a bit of a can of worms. Think I might need to involve an SE. while it will only be 30m2 or just under I think if it joins a house it has to have b.regs in England?
If his vents sit 25 or 30mm on top of fascia thats where you problem is. You could get him to cut a fillet 30mm to nothing over the length of a few tiles say 1m and fix to top of your fascia. Or you could have the over fascia vents extended along your fascia. Or neighbours fascia could be dropped the thickness of the vents but seems extreme.
I just meant supply and fit of the supply and returns not the ufh loop. I didnt realise a plan or drawing was needed to route these 2 pipes thinking you'd just take them straight to where they need to go but sounds like @Mulberry View has to run through the floor?