hi darragh
depending on how thick they are will depend on the best method. you can use your manual tile cutter but you'll have to try one first. if you can't cut them on the dry cutter, stick them through a wet saw. get a glass blade, and dont push them through to quick. watch your hands and finger because the wet fine glass can really cut into your skin. i always wear gloves and dip them in a clean bucket of water after they've gone throught the wet saw just to clean them off.