Parents' names (and then only the fathers) were not included until Civil Registration began in 1837. The marriage record states that they were both of the Parish (Stoke Damerel), John was a labourer and there was only one witness - Wm. DOUBT.
The 1851 census gives John's age as 48 born Plymouth and Sarah's as 43. also born Plymouth.
By 1861, John's age is 58 b.
Sourton, Devon, and Sarah's age is 51, still born Plymouth.
There is an OPC for Sourton, who offers free look-upus - go to
http://genuki.cs.ncl.ac.uk/DEV/Sourton/index.html and scroll down to Genealogy for the link.