Hey, welcome to amiga.org :pint:
Good to see more Sydney-siders on here :-)
Your A1200 should boot straight into Workbench from the hard drive. If it goes to the 'insert disk' screen, well then either your hard drive is dead, or it needs to be formatted. Did you ever have the HD working? If you've got the Install disk from Workbench, boot it up from that and run the HDToolbox program, and see if it finds the hard drive. If it doesn't, either a cable has come unplugged, or your HD is dead. The 1200 and the 600 both use standard IDE 2.5 in hard drives, so you can get any old laptop HD and chuck it in (up to 4gb).
If that doesn't help, I could possibly come and help you set it up, I'm out near Penrith. Hope that helps.