It was behind a brick fireplace with one half of the double socket sticking out. This didn't seem right to me so I paid an electrician to move it, he pulled out brick, chopped into the wall and moved along. The fire place isn't near a corner.
Yes I have got floorboards.
Do the wires need to be relocated then, if not could I put some sort of blanking plate over the old box instead of plaster?
An electrician moved a wall socket along a few inches for me. Is it safe to fill in the hole (using deep gap polyfilla) even though the old box/wires are still there? See pic.