This one has been asked before but there is more. I have just replaced the lights in a house in Spain and they have been inspected and signed off by a Spanish electrician but there is a problem with the low energy bulbs that the owner of the house wants to use. When they have been on for a while and then switched off they flicker (this is the question that you have answered in the past) the switch is new(standard on and off no dimmer) and so is the wiring and the lamp holder. In Spain the way things are wired is there is a main circuit for the sockets and one for the lights and each light or socket is on a spur from that main circuit. All of the wires are run throw plastic tube called macaroni, 2.5 multi core for sockets and 1.5 multi for the lights. When I check the voltage at the lamp holder with an AVO when the switch is in the off position I get 77 volts if I disconnect the switch so the live feed to the lamp holder is broken I still get 77 volts. The house is earthed with a 1.5 M copper and steel rob driven into the ground and all of the earths for the house are connected to this via a 6mm multi cored wire. It is a radial main with no return to the consumer unit. Unlike most houses over here it has a duel pole mains switch (they like to use a single pole mains switch on the neutral side).