I think I will stop doing consumer unit changes had a pig of a job today. Had open circuit on cpc on ring main so left this circuit till last after taking all the sockets off which was a job as every screw was a nightmare to get undone. Any way after a bit of testing found cable was open circuit between consumer unit and first socket. There was a mirror hanging above consumer unit box, thinking this could be where problem was tested and resistance between cpc a nail was 3.5ohms. So chopped wall out and found nail had gone into cable. Stripped back a bit but cpc was intact. Capping and cable where very black though. Pulled cpc and about 3'' came out so chopped wall further up and found another hole in cable. This time it had been phase to earh and had blown cpc in half. Did a temporary repair and said I would have to come back at a later date as it was 8pm. Maybe it was because its Friday 13th don't you hate days when things go so wrong.Batty