Researching Robert Hodgson

I am a newby researching my Grandfather Robert Hodgson b 1828 Lumley Co Durham England. Died 16 Dec 1893 New Zealand. The only info I have on Robert is he was a Coal Mining Engineer in Cassop Colliery. Son of William Hodgson and Ann Embleton. I am unable to find him on British Census after 1841 with his Widowed mother and siblings in Kelloe. His Marriage to my Grandmother Bridget Gallagher states he was never married yet he was 50yrs old, I can not trace the date he arrived in NZ. I have a feeling he may have actually been married before he left Uk possibly to Sarah Hepplewhite. Some of his Family emigrated to the USA. I'm wondering if he may have gone there also ,before coming to NZ maybe via the goldfields in Victoria Australia. A very big ask as I have now hit my brick wall.

Earlier Ancestors in Durham seem to have included the name of either Reed or Embleton. which my give a clue.If anyone can help me with this I would greatly appreciate it thanks. Maryanne