Thanks to Pumpkin Patch from http://www.simplesavings.com.au/, I now have a name for this critcher!
Drumroll please.....it is the larvae of a Large Citrus Butterfly also known as an Orchard Swallowtail.
The adult butterfly looks like this
Rob Bob also from Simple Savings calls the caterpillars "bird poo"
Thanks for your help PP & RB - Cheers