I have a two year old dual flush toilet cistern and after flushing, the water carries on dripping into the cistern and then down the back of the toilet. There is a small polystyrene ball on the left hand side and a plastic "float" on the right.
Thanks
Polly

Polly, November 2008

Sounds like the float is set to high, so it is not cutting off the water supply at the correct level. Look to see if there is an adjusting screw on the float valve. If worse comes to worse you may be able to bend the arm of the float ball down, so that the float does not come up so high.

Rob, November 2008