Hi , I am trying to wire up a dimmer switch. The original one was taken away while decorating and now I can't remember the wiring sequence!! There are two sets of lights controlled by a 2 gang dimmer. In the wall box there is a 4 core cable (Red constant live , Yellow, Blue and earth) then one three core (Black, red and earth) for one set of lights and then the same for the second set. On the dimmer there are two sets of L1, L2, and common. What goes where???