I've moved into a new property and trying to install a new electric fire. The fireplace is already installed in the room and has been for some years so I thought I would just pop a electric fire in the hole. Unfortunately the hole in the middle i.e. the marble is about 10mm too small just at the top for the fire to fit in to. I can't take the marble out as it's all stuck to the wall. So, how can I but a small ammount of marble away?? Angle grinder??