Can't help with the birth date, however I note that he was born in England.
Other information that may assist is that he died during practice for the Natal GP in a Lotus 24 on 22 Dec 1962.
He is buried in the Christchurch cemetery, I can only assume this is the Christchurch near Bournemouth in England.
A Nick Taylor is also writing a biography on him, unfortunately the only contact I can give you is this exchange on a bulletin board,
<A HREF="http://www.knowhere.co.uk/board/kb3314/">http://www.knowhere.co.uk/board/kb3314/</A>
It is great that these famous riders are never forgotten, good luck with the book.