I am also a descendant of William and Jane. My maiden name was Tonks. My father Jack Tonks deceased 1986, grew up with his family in Miramar, Wellington. Survived by a younger sister Marjorie Jane Clarke and older brother, Hylton Tonks, both still living in Wellington. Their father was Henry Tonks and grandfather Enoch Tonks.
Hylton Tonks's son Gary Tonks (my cousin) has done some extensive research into the Tonks line he has traced William & Jane back to the 1600's Birmingham, England.
I believe he has published a copy of the family tree in the Wellington library. I don't know how current that particular copy is.
If you wish to acquire any further information contact me at my email address above.