Why would the staircase person highlight something that he didn’t do had no input in?
he’s there to fit the staircase as it was designed not offer design opinions?
If you can returb to have the boiler, cylinder on the ground floor and create a small plant room/utility cupboard, it will be easier to modify pipework/cabling in future.
plus one to all the other sensible suggestions!
Wouldn’t you want to fit as much PV as possible for example 5kW and let the inverter limit to the DNO max figure, pretty sure that’s what most people are doing these days rather than the original installations of 2010/2011 FIT where it was DNO max limit and that was that
https://www.aico.co.uk/wp-content/uploads/2021/06/Ei3024-Ei3016-Ei3014-Instructions-1-1.pdf
for some good reading
heat in kitchen
smokes in hallways/landing.
and or follow JohnMo previous post. In adding to living room etc
if in doubt run 3core and earth to points and leave an unbroken loop behind the plasterboard for future use