Have a look here James ,
http://www.rta.nsw.gov.au/registration/ ... _faqs.html
I'm assuming your's areen't personalised plus but are only personalised , best check with them in person as I'm sure they'll make it difficult for you unless they get a decent transfer fee .
From the FAQ's
Can I give my plates to a friend or sell them?
Only personalised plus plates can be sold or transferred and transfer fees will apply. All other number plates are only transferable to immediate family members, de factos (including same sex) or between vehicles owned by the same company.