Hi Rap
Civil registrations commenced in Victoria on 1 July 1853 so it would appear that your ancestor's marriage may be one of the many parish records that didn't make it to the Registry for transcription. You are fortunate to have the marriage record in the family bible.
You are looking at immigration at the time of the gold rush and many arrived in Victoria via South Australia. Unfortunately many immigrants were just noted as X number of men, women in steerage.
I have a copy of a letter written from England in 1852 which states that the author was unable to procure a passage to Australia because of the numbers emigrating hoping to find gold. He just wanted to join his parents in South Australia. I sense from other comments in the letter that passages were available for a price.
There are these two births on the Victorian indexes with
Samuel BASSETT as father - you may have already found these

Might be worth following up.
BASSETT Prudence Ann
Father Samuel Mother Ann HOKEDAY
At Sandhurst 1855 Reg#8846
BASSETT Daniel
Father Samuel Mother Ann HOCKEDAY
At Sandhurst 1857 Reg#3639
One of the certs should give his place of birth.
And then this death
BASSETT Samuel
Parents unknown
42 Born England 1862 Reg#3308
Cheers
Cando