1 good reason for checking for wires under the plaster:

I was screwing into the wall to fit an extension lead to the wall, but didn't check for the location of the wire feeding the socket for the Oven!
I'm slightly shook up, and shaking a bit, as I got quite a nasty shock from it.
Some more pics:



You can't really tell from the pictures, but it's cracked the plaster right upto the fuse box at the top of the wall, and as you can see, it's come off in quite a few places.
:oops: