This is very frustrating - I have put a junction box on a twin and earth1.5/1.0 supply feed cable to get power into the loft for a light. I then fed that new cable to a 3 plate ceiling rose and a cable to the switch - all cables are 2+E 1.5/1.0. The pendant has a current and the switch cable has a current but the bulb won't come on ...What have I done wrong?