Find Ancestors

Greetings from Tasmania! I am trying to find my husband's father, William JOHNSON. That's about it, folks! Can anyone help with ideas on what to do with just a name on a birth certificate? My husband Jack was born in Leicester in 1936 and I have found an electoral roll reference to William and Violet Evelyn JOHNSON living at Day St, Leicester in 1936, but nothing before or after that year. Violet reverted to her married name of COPSON after the war and lived at another address but William never appeared with her again. Violet was born in 1903, so we assume that William was about the same age? He may have gone to live in the Knighton area and married and had another family but that's all the info we could prise out of Mum before she died in 1985! If anyone has any ideas of where we can go now, please give us a shout! We are currently in England on a genealogy safari until Sept 26th when we are headed back Down Under again, so any help would be most appreciated! It would be marvellous if we could even just visit his grave (as we're sure he would be dead by now) Jack and Jill JOHNSON Sorry! Should have been more specific! William and Violet never married, that's what's making this so hard! Violet was born Green and married Harold Copson, whose name she kept until her death in 1985. Thanks to those with suggestions so far. Every little bit helps!