Very interesting information from people who knew David Denny, particularly those who were at school with him at KCS Wimbledon. That he was killed in a road accident only two years after Sandy Denny's tragic death at 31 is particularly poignant, especially if the Dennys (Neil and Edna) had no other children. Did David Denny marry and leave any children? If not, Georgia Lucas is the only descendant (and now her own two daughters).
At least the family was able to have him buried next to Sandy.
The Heylin book no doubt has some information, but is regarded as rather poor (or unsympathetic at least). Amazon.co.uk lists a new biography of Sandy Denny to be published on 5 February 2015 (an unusually exact date). It is by Mick Houghton a national newspaper music writer. If the Estate of Sandy Denny has 'authorised' it we should find out more about the Denny family then.