I'm wiring a new light in a bedroom. I've used a fout block connector and put all the red wires together, two black wires are together and the what I think is the swtched live (alos black) and the earth both have a block of their own. I've connected the light's live wire to the switched live and the lights neutral wire to the to neutral wires block. THe light doesnt work. However if I change the black wires around in case i've got the swtched live wrong the rest of the lights on the upstairs floor dont work but the one i'm fitting does. Any ideas anyone?