We were having a house built and the builders have gone bankrupt so we have been left to finish everything off ourselves. The plasterboard walls have been put in and the wires are behind the walls for the electrical sockets etc but they haven't been pulled through externally. Can anyone tell me how we locate these wires? We know that we can use a stud finder to locate the beams etc but not sure how to find the switch plates for the plugs etc. Someone suggested we use a magnet and pass it along the wall and we've tried this with a very strong magnet but it didn't work. We really don't want to start knocking holes in the plasterboard unless we're sure that the switch plates will be behind it and we have about 70 to locate. Any help would be appreciated - thank you.