Voyages to London, England

My great grandfather Helge August Olsen Myhre left Stavanger and travelled London where he eventually lived and married. Probably between 1848 and 1855. We have no idea how or when he travelled. He was born in Drammen in 1831. His father was Ole Hansen Hansen Myhre married to Sara Marie nee Stoltenberg. Any information would be helpful. Phil Myhre Auckland New Zealand