Hi Nicole - Hope this is of some help.

Although, there is New Passage Hill in Plymouth, Devon, it is more likely to be New Passage, a small hamlet in South Gloucestershire
http://en.wikipedia.org/wiki/New_Passage
(aka New Passage, Pilning, Bristol)
http://www.genuki.org.uk/big/eng/GLS/Henbury/Gaz1868.html

Many people departed England from nearby Bristol Docks.
http://en.wikipedia.org/wiki/SS_Great_Britain

http://www.bristol.gov.uk/sites/default/files/documents/leis...

http://www.theshipslist.com/ships/australia/SAassistedindex....

1851 Census: Thomas Wilson 3 Scholar Gloucestershire 1848 Bristol
1851 Census: Thomas Wilson 2 At Home Gloucestershire 1849 Bristol
Guess he was entered twice as I can only find one likely birth...
http://www.freebmd.org.uk/
Births: Jun 1848 Wilson Thomas Bristol 11 152
Good luck. Sue