I am hoping to trace my dad - name is Dennis Knight - Welsh background- how can I find him?

I live in Australia and am now 49 looking for my dad who gave 3 of us up for adoption in 1974. I know he was in the RAF, lived in both Bristol and Holbrook and was married in a church in holbrook to sheila vockings. Any suggestions on where to start looking - we are a long way away!!