I have removed a strip light and replaced it with a ceiling rose and bulb holder, the wiring was straightforward as there was just black, red and earth. The new light doesn't work, with a tester held against the wire between the ceiling rose and bulb holder shows current when the switch is turned on, but the bulb doesn't light. The bulb is OK, and I can't work this one out. I don't know if the strip worked before removal.