The startup file has loads of other stuff in it that it won't let me delete, none of them are commands which you have listed?
Hmm... Won't let you delete? What program are you using?
Anyhow, that doesn't matter too much. It sounds like the installer installed the wrong s:startup-sequence file.
Boot your Amiga from the Hard drive up to your command prompt, and then insert the "Workbench 3.0" floppy in df0: and type the following command:
sys:c/copy df0:s/startup-sequence sys:s/startup-sequence
Type 'y' to confirm replacing the existing file.
wait for disk activity to stop.
remove Workbench disk from df0:
CTRL-Amiga-Amiga to reset the machine.... and viola, Workbench. hopefully. ;-)