I have been researching Bullens in Australia and last year was in touch with a Steven de Grussa who had some information on your Samuel and Elizabeth. At the moment I am in Western Australia and don't have my Bullen research with me. So if you haven't already been in touch with Steven, you should be able to find him fairly easily through the Rootsweb message board for Bullen around June or July 2005.
I have been searching for John Bullen and his wife Martha King who came from Oakington in Cambridgeshire in the 1850's. Apparently they too lived in South Australia for a couple of years before moving to Bendigo Victoria.