Help with fault on light

[novice1234]

In process of updating flat so I can move in but got a prob. In the bedroom, I had a dimmer swich installed which has been working fine for months. I recently had to have my ceiling plasterboarded and replastered, after which the light is no longer working. Plasterboard was nailed into beams so unlikely that any wires have been tampered with. Position of light had to be moved to centre of room and so wires were extended. I've made a small hole where the wire extended box was and there was a loose wire, but even after tightening it, there is still a problem. Out of the 3 wires, there was power to 2 of them intially, but not to the black wire. When I checked power at light switch, it showed that there was only power to one of the wires, which I found was correct when I checked the wires at the light switch again. Wish I had taken a pic as can't rem which wires did/didn't have power off the top of my head. Can anyone help with suggestions as to what I can try without having to call someone to take a look as am scared I will have to break plaster off ceiling/walls. As a last resort I may have to do that, but am trying to avoid at all costs at the moment. ANY advice appreciated!!!

 

[Steve]

Where you extended the cable - can you get to this joint?

If not, why did you see fit to hide it?

The wiring regs state that all screw joints must be accessible for maintenance.

Anyway, how many wires went to the light to start with? And how did you connect them to extend them?

Has the circuit tripped at all during your "fault finding"?

 

[securespark]

Post some clear close-ups of wiring, please.