Roland I have been in touch with Suzanne and confirmed that we are 1st cousins our fathers being brothers, although we lost touch some 30 years ago on the death of my father.
You are correct in what you say from Henry onwards, I havecopys of the birth and marriage Certs From Stanley Leonard Dudney B:Plumstead 8th July 1900 back to Henry B:Woolwich 25th June 1839, He indeed married Jane Horsley (father James Horsley a servant).
Henry had an older brother (prior to 1837 birth certs) called William, baptism record for the parish of Woolwich kent number 1384 shows William born 30th July 1833, Son of William and Martha Dudney living in Rope Yard Rails Woolwich.
Your William from croydon would have been to young (13)
Also William Dudney B:1805/06 (1881 census living in East Wickham Wife=Martha Padgen ) Father of Henry, His parents are very likely to be William Dudney and Mary Ann Johnson Married 1801 East Wickham (IGI)
Roland you are likely to be related to us and possibly John dudney who posts on here ( Erith connection ) its just finding how far back.