Thanks to those who stopped for me this morning. Turned out just to be one of the bolts that holds the seat on and in position snapped clean off, Lucky I was close to home but drivers seemed to have a good laugh at the train crossing at the fact my seat was hanging off the back. Have picked up a couple new bolts and apparently these ones will hold the weight of my fat ass,

Couple photos from when I got home for your enjoyment. http://www.lionslair.net.au/2012/06/30/ride-ruined/