How to connect when there are 2 cables of ceiling light
This is a switch leg or that’s what we call it on this side of the pond.
How we would wire it here is to connect the hot or L of the consumer unit to one of the wires going to the switch then the line coming back from the switch is the switched hot L. The switched hot goes to the L the N from the consumer unit in the n and connect earths
I did not put colors in since you did not mention them and I believe there are 2 or 3 possible combinations based on when built.
The wire going to the switch with the consumer unit hot we would use our normal color wire for N or white so that line is always hot and the switched hot brown or whatever is hot when the switch is on but the neutral always being hot can’t be mixed up as a neutral then we put tape or mark it as a hot.