My understanding of a C2 on an EICR means that something on your installation is POTENTIONALLY dangerous

To my mind it's a bit more nuanced than that - yes, something C2 is potentially dangerous, but not everything that's potentially dangerous is a C2. A BC or ES lampholder is potentially dangerous (you can put fingers on live parts), but not codeable at all. My personal rule of thumb is to think about the usual levels of shock protection (i.e. we typically ask for two faults to danger) - no protection (e.g. exposed hazardous live parts)  would be C1, lack of a 2nd layer (e.g. lack of earthing or double insulation, but basic insulation intact) would be C2, lack of 3rd layer (e.g. additional protection missing, but ADS/double insulation OK) would be C3. Of course, there are exception (or refinements) to those rules, sockets feeding extension leads outdoors would be a C2 rather than C3 without 30mA RCD protection as the length of leads means you can't control Zs and therefore guarantee ADS (quite apart from the lack of additional protection per se). Likewise lack of additional protection in bathrooms (both RCD and supp bonding absent) would be a C2 because normal ADS doesn't provide the same level of shock protection in the wet/naked/barefoot conditions.

I'm quite surprised that a DB or CU lacks an indication of which way is off - it seems to have been the norm even going back to the days of cast iron side handled fuse boxes. The Wylex CUs often had a bit of loose plate hanging on the switch dolly just behind the front cover that would indicate ON/OFF in the bit of the hole the dolly wasn't covering - loss something of that might have more implications in that internal parts that should have had some covering could be exposed. (Like loosing the coloured dots from rewireable fuse carriers - which left a live fixing screw exposed.)

   - Andy.

Well put - agreed!

Well put - agreed!