Using 3 core and earth cable with brown sleeving on the black and gray cores you connect all the terminals like to like. i.e. L1 to L1 and common to common and L2 to L2. Which ever switch the switch cables from the light arrive at these will go to L1 and L2.
Note:- This is not the way shown in things like Wikipedia which will show school boy method with the switch wires going to the two commons this method is not used because it requires a junction block in the switch.