I'm afraid I can't help with the NZ part of William's life. He was born in Greenock on the 13th May 1834, the son of William Caldwell and Agnes Rowan. He was indeed a grocer, but in the Anderston area of the city of Glasgow, not in Greenock. In 1871 he was living with his wife Margaret and 3 daughters in Perth Street, Anderston. By 1881 they had moved to Hope Street, Anderston (nowadays known as Anthony Street), and a son was now living them, as well as William's mother.