I have a fairly new bathroom suite. The toilet seat has a nifty quick-release hinge which allows you to just press two buttons to take it off for cleaning. Underneath, the hinge assembly is fixed on with a long screw, tightened with a nut that fits snugly into a recess inside the porcelain. There's no screw head accessible from underneath, and the hinge doesn't come off on top to screw from that direction.
Naturally, the seat has come loose. How do I tighten it? I've tried just turning the screw thread with a pair of pliers, but it's hard to get a decent grip and this only works for a short while. Is there a particular tool I need to buy to tighten this sort of screw? Or a particular technique?