More info - judging by his death certificate - William was born in 1825 - though I have no idea where - on his marriage certificate his father is listed as another William Greenfield, also a plasterer.
William's wife Susan, judging by her death certificate, was born 1828 - a 13 yr old Susan Lewin and her parents Samuel (a carpenter) and Ann Lewin are listed as living in Brook Street, Hackney on the 1841 census.
William and Susan were living in Brook Street when they were married in 1848, however later they are living in 7 Wood Street, Hackney - their son William was born there on 01/05/1849.
In 1852 they migrated to Wellington aboard the ship "Ann Wilson" - a horrific journey with many deaths on board.
I think Susan's eldest child, a daughter had the surname Lewin -on his death cert, William died 27/04/1885 in his residence in Tory St - he left "a grown up family of 8, several of whom occupy respectable positions in the town (Wellington) while others are in Australia - Henry, my g g grandfather was born Wellington 21/03/1864.
I have no idea where the Greenfield's came from before Hackney - but would be very interested to find out.