External wiring help needed urgently.

[Spark123]

There are no neutrals present at the switch, all the terminals with two wires in are the feed wires.
The black wire in there is probably part of a 2 way lighting circuit.
The individual wires (only 1 per terminal) are the switch wires.

It may be better to call out an electrician now to come and disconnect it so you can at least have lights back on tonight.

 

[DetlefSchmitz]

... or clean out the hole in the brickwork, push the (new, clean) connector block into it, and fill with silicone sealant.

'Ordinary' silicone sealant gives off various vapours (acetic acid and probably also water) whilst curing. Once cured, it's fine, electrically, but IME if one smothers a connector block with it, there can be quite a low 'insulation resiistance' (sometimes enough to trip an RCD) for the initial day or three.

Kind Regards, John

Been there too!

 

[ban-all-sheds]

I seem to recall a figure of 45kV/mm. That's not insulation?

It does not comply with the requirements in BS 7671 for insulating material, nor does it constitute an insulated enclosure.