Hi Gerwyn
Very nice work
I like the look of your heater box cover. I'm in the process of tidying mine up. I couldn't powder coat it as it had a small dent in it from new, so I filled the dent and rattle canned it black - looks OK, Like you I will replace the rusty mild steel self-tappers with SS, but intend to use socket screws into rivnuts.
Particularly interested in your SS mesh, at the moment I intended to use PC case filter material. May I ask where you sourced yours and how you secured the rear of the mesh?
Also did you have some foam draught excluder between the box and the bulkhead? If so have you found anything more suitable to replace it with?
Brian