Hi liz and Geoff,
Thank you both for your help with this, I really appreciate it.

Hannah and Joseph Hopkins came out to Australia in 1855 with their four children: Joseph Jnr, Mary Elizabeth, Benjamin and Keturah. I'll order the Marriage Cert like you suggested and that way I'll know who her father was.
Thanks also for looking up all that information on Keturah liz. The other side of my family comes from Leeds.