My brother has in his dining area a central light and two wall lights. They
were operated from just one two gang wall switch, (i.e not 2 way at opposite
ends of the room). He wants to change the rocker switch to a 2 gang dimmer.
He asked me to do it for him and I said I could go over tomorrow night. I
told him not to touch anything until I got there. He has just rung me and
said her indoors wanted it doing tonight so he stareted it!!! He wrote down
the connections and then removed the switch, he took out the new switch (2
gang 2 way dimmer) and looked for his drawing. Unable to find it he asked
wifey if she had seen the "cash machine slip that was on the sideboard", she
replied "I've shredded it, you're not supposed to leave things like that
lying around!"

I will go over tomorrow to hopefully sort it but I am not a sparky and
usually change my light switches etc in the same 'make a drawing' style as
above. In the wall back box he has a T&E and a single core grey sheathed
cable. The new switchplate has L1, L2 and C on each switch (obviously).
How do I wire it so that one switch operates the wall lights and one
operates the central light, everything worked perfectly until he 'forgot'
where the wires went, so I don't need to lift floorboards etc to get to the
junction boxes etc.

My thoughts a
Red to C (then strapped to other C)
Black to L2 (on the same switch as the T&E Red)
Grey single to the other L2.

Is this correct? If not could somebody help please, I do not want to spend
all night at my brothers listening to SIL saying "Is it done yet?"

Cheers

John