Hi, i had a 1 gang switch upstairs and a 2 gang downstairs.
They were wired like this:
Downstairs on 2 gang
L1 = Black
L2 = Empty
C = Blue
C = Red (From red, black and earth wire)
L1 = Red (From red, yellow, blue and earth wire)
L2 = Yellow
Upstairs on single gang
C = Blue
L1...