We did have to show our driving licences too, we had to go and get them quickly! Don't know what a customer reference number is though either! Maybe it depends on the garage, don't know; we've bought three cars now, and had to show our licences for all three. It doesn't take long to get one though; just go into a Queensland transport office, show your U.K licence, evidence of identity, evidence of QLD residence, hand over some cash (UNBELIEVABLE!), and they give it you there and then.
Driving in Queensland with an international licence
This link explains how to get your new licence. You could hire a car for a day or two, and then get your licence ready to pick up your new car.
Jo