Firts clean off any rust from the threded part, then put a screwdriver ( or similar ) between the top of the wing nut and the toilet pan, to but a downward force on the wing nut, then unscrew, at the top end of the bolt, the wing nut is on, it has a squard shank that locates into a metal slot, if this dose not work, cut between the top of the wing nut and the toilet pan, you will have to grip the end of the thred when cutting the bolt
Chris, November 2009