I have had another look at this today.
The lightswitches have metal back boxes. The wires enter the backboxes from within the wall, the end of the cable is inside the wall. The connection between the cable and backbox is not visible, but there is a connection as the backboxes are connected to earth somewhere.
There are no grommets, the wires just come through a knock-out hole in the metal.
The sockets have a similar arrangement, with the earth being a short length of wire attached to the backbox with what looks like a woodscrew. Under the floor the joists are notched and the cables just laid in, so the cables are in contact with the back of the floorboards.
As for the lighting, the pots at the ends of the cables are clamped onto the back of a metal box which is behind the black plastic rose as shown in the photos, there are evidently connections inside there.
I have not removed any of these as the wiring is fragile enough already, but looks like the standard UK loop system (in/out/switch).
The location is in Bournemouth, so about as far south as you can get. The grey/white cable is certainly true, until a few years ago grey cable was a rarity here.
The property is currently rented out and allegedly had an electrical inspection done 18 months ago. Of course, no documents exist regarding that or any other inspection. No labels on the CU either, personally I don't think anyone has inspected this since it was installed.
The lighting on the 30A breaker is a recent change - someone has connected wall lights using 1.5mm twin&earth directly into the back of a socket outlet, from there to a junction box with further T&E cable to the lights and the light switch. No fuses anywhere, and the light switch is a 2 gang one, one gang on the the original 5A lighting ciruit and the other from the 30A ring final.
