idel standard cistern will not stop filling?

Depends what fittings you have inside the cistern.
You might have a flush valve - which is a
'round cage', with the mechanism inside it.
Hold up the float arm, after flushing,
and carefully twist the cage - it should be a
bayonet fitting - take care to twist the correct way.
Lift out and check that the black silicone washer at the bottom is not damaged or covered in deposits. Wipe off, reposition and re-fix cage.
Alternatively - as you probably have an internal overflow - the water level in the cistern is too high, and you need to adjust the screw and nut on the top
end of the float arm to reduce the water level in the cistern, so that the overflow level is not reached.
If you need a new washer for the flush valve, try
Grahams, or contact Ideal via their website

Beentheretoo.
April 2009