Sorry, yes 2 core and 1 earth.

John just to confirm, I take it doesn't matter if the red/black/earth
earth wires are running back to a switch (Method 1) or a junction box
(Method 3) as this is the supply regardless, correct?

I've had a look in the double switch, there are 3 cables entering it,
2 of which run to a pendant and the other I presume is the circuit
cable?