How to add a plug socket in a specific scenario

Question

Not sure if there are any UK electricians on here, or how similar the electrical industry is to the American system, but here it goes...

I recently moved into a flat in London. A combination of being inquisitive and being too broke to pay for an electrician has prompted me to try and install a new plug socket (outlet?) within a wall in a cupboard. The person inducting me into the new flat pointed to a plate with no interface (just a flat plastic panel with screws) and said "if you want to add a socket in this utility cupboard, that would be the place to do it".

Here is a quick illustration I did of what he was pointing at:

The plate without an interface was the one he pointed at, but the ventilator switch becomes part of the story.

So I went about unscrewing the plate and taking a look at what is underneath it. I thought it might be a simple case of buying a socket to replace the blank plate, and fixing some obvious wires to it.

What I saw when I opened the plate was a load of grey cables connected to a connecting strip on one end, and a flex cable connected to the other end. Some of those grey cables are coming from above, and some (on removing the ventilator plate) I can see are going into the ventilator switch.

The white flex cable travels north up the wall - and I presume it is the ventilator - but it has a fourth flex core (black) going into the connecting strip. On close inspection of the setup, it all got a bit confusing.

I have drawn a very accurate illustration of the setup (note all the wires are going exactly where they are going in real life). I decided to illustrate it (rather than take a picture) because a photograph cannot describe the complex setup. Note that blue is neutral, brown is live and yellow is earth. I have no idea what the black cable on the 5-core flex is; or what it is doing.

Can anyone make sense of this setup? Where would be the best place to put a plug socket (outlet) and would I need to reconfigure anything to do so?

Any help would be super appreciated. Thanks in advance.

Answer 1

Although I'm very curious as to exactly what is going on here, in answer to your real question:

1. This is probably on a lighting (or similar) circuit, which would make it unsuitable for a plug anyway. You could test this by turning off your breakers one by one and figuring out what's on that circuit. If the wiring is up to scratch, all wire under that circuit should be sized appropriately regardless of its actual use.
2. However, even if it is suitable for a 13 amp plug, you won't have enough space for all those wires, a block connector and a plug unless it's insanely deep behind there
3. Blanking plates aren't generally put in "just in case" - it's just as easy to cut the wire and put a socket in, the hard work is getting wires to it and the backbox in. They're normally either left over when something is removed (Such as a hard wired appliance) or, in this case, when the electrician needed somewhere accessible fro a junction box. It was not envisaged as a place for a socket.
4. Given the above, the complexity of what you're looking at and the fact you're unsure (And I'm just some guy on the Internet guessing) you MUST get in touch with an electrician to investigate this further. You're in this because you were under the impression that it was an "obvious" place to add a plug - I'm telling you that this is probably not the case.