Take it back, my halford set has some spark plug bits in there and they fit down to get the old ones out. (mk2 16v) Measure the bore of it then measure some of the others they have in there to get the right one.Nothing worse then getting back and the tool doesnt work though
Yup 14mm but you need a thin wall socket rather than standard 14mm socket. I had the same problem with abf. Halfords sell the socket.