After turning off your water you need to bale water out of cistern then unscrew the cistern from the wall.
Disconnect the inlet supply and the overflow connection.
If you look underneath the cistern where it joins the pan you will find two bolts(close coupling bracket bolts)undo them evenly and gently lift cistern away from pan.With cistern on a flat surface undo the large cistern backnut that holds the close coupling bracket and syphon unit in place.
Steve
November 2007