Fit a shower pump into the cylinder cupboard. Single impeller if your cold supply is mains pressure, twin impeller if it is a cold water tank. The negative head ones have a small air chamber that pressurises when the flow stops so the pump will be ready primed.
Smell is very difficult to establish and prove. Actual moisture and mould can be measured and photographed. Have you had anyone else in to verify the smell, like a mate or your partner? If it is really obviously bad you should go back to the housebuilder and register it as an official issue, stating that x people have also noticed it.
The stainless steel ones seem pretty good. I had one fitted and it stopped the rats and has not caused blockages. Some of them have a mechanism that allows them to be fitted fairly deep in an inspection chamber.
We put standing seam on a roof and the customer had solar added. The were fixed by brackets that clamped onto the standing seams. The roof actually had a slight fall to north but it still worked fine. The standing seam was Kalzip type.
Agree with @Spinny if the rule was not around until 2023 your steel was already in. Point this out to BC. You can't comply with rules that did not exist at the time.
I think the rules are about right. The planning officer can ask for further details of anything relevant if required. Measuring and detailing the height and position of all surrounding buildings, rooflines, eaves, windows, ground levels etc. is pointless for most applications.
It depends on what is around you. Sometimes full elevations of nearby buildings, always drains, covers, inverts, pylons. Our architects just use 2D as you don't gain much with 3D and it adds to design time.