Thanks for that terrific reference, bearkat. I have been busy looking at some possibilities, but no luck so far.
I was aware that two of William's children, Henry and James, had also used other surnames from time to time, and hoped that one of those names might turn up a marriage for William.
The main alternative name is Dunmill, which Henry used as a middle name at his marriage and when registering a number of his children in South Australia. Both Henry and James came to S.A., but James used Dunmill exclusively as his surname here, with Paddick as a middle name.
The other possibility is Sealy and its variations. James Paddick married Ann David at Maidstone in Dec 1833, but a month earlier a James "Sealy" and Ann David were witnesses at his brother Henry's marriage. One of Henry's grandsons later adopted the name Sealy as his christian name, although it was not registered.
Furthermore, I had been unable to find Henry and his wife Maria's first three children in Kent under the Paddick/Paddock surname, but there are three who fit perfectly under the names Seeley/Sealey/Sealy. There is also a daughter of James and Ann Sealy christened in 1836.
There don't appear to be any other "real" James or Henry Sealys in the area at the time.
If you're confused by all this, imagine how I feel!
I guess it will all come back to William's or even Philadelphia's parentage, which I still don't know. With the possibilities of mother's maiden name, illegitimate birth and subsequent marriage, or legitimate birth and a later stepfather.......
The way things are going, William might have married under another name I haven't come across yet.
Didy