We're curently doing over the house and replacing cisterns with modern top press dual flush ones. The suite in the main bathroom is about 20 years old but is still extremely good looking. The cistern currently has a flap valve operated by a push button where the side lever used to be. Would it be possible to core drill the cistern lid to take a top fitted dual push button. I imagine it would be rather like drilling a hole through a thick tile. Has anyone attempted this with any success.