Thanks for your answer mate. The alarm has to go because my girlfriend wants it to go, because it's old. I'm worried that i could be next LOL. I will replace it. The alarm is above an airing cupboard door fixed to blockwork [concrete] and obviously the plaster on top of that. The fuse box is inside the cupboard so the wires go through the wall. Using your method i could pull the wires through the wall and fit the choc box inside, then fill the hole. Would it still be ok to do this if something else is on that main, as long as i isolate it? I'll see if i can get a photo later this morning. How would i upload it?