Hi Robin I'm in Adelaide as well, and for the last 7 years have been doing free lookups for people wanting information from the records here re their ancestors who came here. I was in the library yesterday and had a look for info. re your Benjamin Shipwright and Sophia Brooker.I didn't find much, and perhaps you already have the following, but here's what I did find.
There are no arrival records for a Benjamin Shipwright from overseas.
Benjamin Brooker, gardener, single, aged 31yrs and William Brooker, gardener aged 40yrs both arrived in South Australia 28th May 1856 aboard the "Eliza" which sailed from Southampton.
There are no marriages recorded here for a Benjamin Brooker/Benjamin Shipwright or Sophia Brooker.
I found the following on the I.G.I. page of the Family Search site.
Benjamin francis Shipwright born 5th August 1826, Christened 3rd September 1826 at All Souls, St. Marylebone, London England.Benjamin was son of John William Shipwright & Charlotte??
I hope this doesn't cause more confusion.If I can help in any other way, please don't hesitate to get back to me.