As you have clearly outlined - William had just one child i.e. Charles William Hammond born 1909 who married Lily Lovatt 1936. Somehow, I don't think the female born 1940 Birmingham is theirs as looks as if that person married there too (1959 or 1960).
However, I feel sure the male born Macclesfield in 1948 is indeed their son - he married 1971 and had 2 sons born 1974 and 1978 (both of whom have the second name William, like Charles himself).
Electoral rolls show this son, wife, and their 2 sons living in Macclesfield until 2014 - cannot see an entry for said son (born 1948) after then BUT the eldest of his own 2 sons (born 1974) is shown as currently living there. This person would be William Hammond's great grandson and one of the closest living relatives (although if his father is still alive he would of course be the closest being William's only grandson) so should surely be the person to contact now??
Hope this all makes sense - difficult trying to explain without 'naming names'.
Annette
