On Wednesday, September 3, 2014 11:25:53 PM UTC+1, Tim Watts wrote:
Each of these 4 locations will be a "cupboard" on the dormer uprights in
some semi dead space (where the ceiling is low) but usefully accessible.

You could use meter cupboards. Fireproof metal box, f/r backing board for fixing things to, and a neat(ish) door and frame with a cam-lock.