UK How best to route cable with minimal damage?

[gezzer]

I'm an Army qualified sparky from the 1970's, but moved out of the industry after leaving, so do not have a high amount of practical experience, apart from work in my own home.

The low voltage halogen light in my WC has failed, however, the mains cable to the transformer is snagged, probably when a plasterboard ceiling was fitted below the original artexed one so by dropping the existing fitting I cannot access the transformer or its feed cable.

I would like to isolate the existing transformer and leave it in the ceiling, replacing the existing light with a mains or low voltage LED, but I need to run a new feed from the pull cord switch and cannot decide on the best route. The pull cord switch is installed below a boxed steel so I cannot drill up from the switch and the side wall is solid brick. The fist picture is taken from the utility room which the WC is off, where the ceiling level is higher, so which could be useful.

What tricks and tips do you experts have for deciding on a route and running cables with minimal damage, and so minimal making good?

 

[westward10]

Is the feed actually at the pull cord?

 

[gezzer]

Wow, that was quick! Yes it is. I have verified that the switch feed in is live and the switch is good.

 

[littlespark]

I think Westy means is there a neutral at the switch as well?

I take it there’s a flat roof above, or no easy access to above the ceiling?

You might have to cut a square out the ceiling where you think the transformer is, and get the cable from there.
Means having to patch the plasterboard, but it can be done… gaps filled, couple of coats of paint, and the join will be almost invisible.

 

[gezzer]

Yes, there is a neutral.
The roof above is a pitched tiled roof on a ground floor extension, which I had thought of but, to be honest, I don't really want to disturb, but interested if that would be the way you guys might go.