Nice post there durham .....proper work great stuff. Not sure if things have changed but in that UPS Battery room noticed the flours and the grid switches were not sealed type, are the batteries then non vented type. I remember at an hospital I did we had to use sealed lights, switches and sockets, but this was a few years ago and may have just been NHS spec.
Not sure also if it's the camera angle but it looks like it would be a bit of a task to replace any of those batteries on the top level as they seem close to the lights.