Moving light fittings in lathe/plaster ceiling

Hi All,
I'm hoping to move some lights in our kitchen. I don't have access to the ceiling from above, unfortunately, so what I'm hoping to do is this:
Take the existing rose off the ceiling. Cut a hole approximately 10x15cm where the rose had been. Cut a 1cm-wide trench from the old rose position to the new position. Replace the 2-core with same, but long enough to reach the new position. Push the old rose into the hole and fix it to the nearest joist/ noggin. Fix the new light in position and run the 2-core from the old rose down the trench to the new light. Fix the hole with a small piece of plasterboard and then fill the hole and trench.
Is this a good plan? When I come to push the old rose back into the ceiling, do I absolutely need to fix it to a joist inside the ceiling?
Cheers - Adam...
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Adam-the-Kiwi wrote:

Not totally.

You need to replace the ceiling rose with a junction box, and run twin+earth cable to the new location, terminating in a new ceiling rose, back box, or terminals wholly contained within the luminaire.
You don't absolutely have to fix junction boxes to the ceiling providing they are supported. Joints must not be supported by the conductors though.
Owain
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In the case of two of the light fittings, there is no earth connection - hence the idea of using the existing rose. For the third, which is metal and hence has an earth connection, I'll definitely use a junction box.

Sorry, don't understand what you mean by "Joints must not be supported by the conductors" (probably due to the time on a Sunday morning!)
Thanks for the help - Adam...
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Adam-the-Kiwi wrote:

There is an earth connection in the circuit though?

JBs must not be left dangling from the wires.
Owain
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There's an earth terminal in the existing rose and the rest of the lighting circuit uses standard 3-core,1.5mm cable. The new lights have an entirely plastic rose and there are only two terminals therein.

Aaah, I understand. Actually, I parsed your first post about 20 minutes after I posted mine - hadn't had my coffee at that stage!
Thanks again for the advice.
Cheers - Adam...
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Adam-the-Kiwi wrote:

You must still run an earth to the luminaire, and terminate it appropriately (g/y sleeving and a piece of choc block)
Owain
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