OK,
I took a fresh copy of Workbench from the original disk.
Copied PC0 file from the Storage3.0 disk to the following:
Workbench3.0:Devs/DOSDrivers/
REBOOTED
At the SHELL prompt types "mount pc0:"
It told me the device was already mounted so I inserted my PC formatted DD floppy and it just came up DF0:

(no other PC0 icon).
I remember this being a lot easier back when I was in collage.
Thanks for your continued help...