i am returning my toilet back after decorating and the push button cistern keeps filling and overflowing back into the cistern

alan white, April 2013

If its over flowing it would not be over flowing back into the cistern that's not possible. Sound like either new washer job or needs adjustment.
Look for threaded rod on the arm a ball type or long threaded rod on the upside down cup type and adjust accordingly. Arm type will have a lock nut slacken that off first.

bob, April 2013