My toilet cistern it leaking into the pan. It has a Dudley Hydroflo inlet valve which I assumed was leaking but it does close properly. If I shut off the water supply to the cistern it will empty itself into the pan in a few hours. Before I pull the cupboard to bits and remove it all from the wall, does anyone have any pointers as to where to start looking in the cistern? Hopefully it just needs a clean around the seals, but is it likely to be anything else? I can't see any markings on the cistern to identify it... Thanks.