Rendered concrete block outer leaf, 50mm cavity, Rockwool insulation between 140 studs, 40mm PIR, 25mm service cavity, resilient bars, plasterboard. Inexpensive and very effective. Less than 400mm.
If that is the case, make no provision for them. Do not suggest to tenants that they are authorised to install batteries. A world of liability for you.
That is dreadful. You need to use the main flow of the chamber for at least one junction. Use a smaller IC, add 45s to the main inlet and outlet. Move the chamber down and right. If you want I can do a sketch.
Ours have key access externally and thumbturn internally but when the door is shut, bolts in the door automatically activate, so if you shut the door from outside you can only get in with the key.
When the plans are submitted to BC they will do a plan check to let you know if they comply. I think that to comply each room either leads directly to the protected staircase or is on a corridor that is part of a protected escape route.
Just get them to hover over your tray and crap the contents out. It is a bit messy but it will be fine. Water dries up, concrete sets and can be broken up.
For concrete I use a sheet of 18mm OSB and some 4 x 2 to form a tray, lined with polythene. Let the concrete go off, then break it up and use it as hardcore.