I'm trying to replace my existing light fitting in the bedroom ceiling with a Kuba mains voltage halogen 4 spot unit made by Ring of Leeds and bought from Focus DIY. The instructions with the halogen unit say the appliance must be earthed but there is no earth wire sticking out of the hole in the ceiling. Its a flat roof so cannot fit an earth. There are three wires coming out of the ceiling and two are bound together. Will I have to take the light back and replaced it with a unit requiring no earth? I rang Focus DIY who said I should screw the earth lead from the light into a joist - can this be right?