Good progress.
So a private investigator was going to be ridiculously expensive so instead I did some googling of my own and tracked down one of my uncles and now after 41 years I am at least emailing with my mother who hopefully over time will share with me more details about my father. The important thing to remember is not to be insensitive and step on anyones toes, your need to know your parentage has to be balanced against your birth families needs for privacy.