Hi there cousin (however many times removed). Presume you reside in UK? Shame we were not far enough down the track with our researches to have been able to connect when you visited NZ.
I recently got William Royse's Birth Certificate from UK GRO, b. 6 Apr 1838 to Isaac Royse (occupation Joiner) and Rachel (nee Darwent), however did not establish details of either Isaac or Rachel's parents. Do you have documentary evidence that Jeremy and Ann (Nancy) Royse were Isaac's parents??
As you no doubt know Castleton was a hotbed of Royse's making their fortunes in the Industrial Revolution from their lead mines. My main source on Castleton Royses is this info: http://genforum.genealogy.com/royce/messages/931.html
but I'm unsure of the accuracy. I'm intending to contact the author and query him and contribute my genes, just haven't got around to it yet.
I'm also interested in the Darwent connections, because when William Royse first went to Australia aged about 21 he soon became a shipping agent in NZ, representing Joseph Darwent, ship owner of Adelaide, who must have been a relative, uncle? http://www.flotilla-australia.com/saother.htm#darwent
Keen to keep this investigation going and unravel the threads, best regards Paul Royse.