Oh Riley! I'm thrilled! Thank you SO much.

I had found all his sons but only two daughters, so I've now got more names to look out for.
The back story ... well, I'm still blundering about! Henry St. Hill (full name
Charles Henry or
Henry Charles St. Hill?) was the Ordnance 'Storekeeper' (officer in charge) at various British army bases around the world, including Jamaica, Ceylon and Hong Kong in the first half of the 19th century. He must have brought/sent his children to NZ even though he was posted elsewhere.
The eldest son, James Henry had trained as an architect and got in with Colonel Wakefield and the NZ Co, arriving in Wellington in 1840 — uh, after he had been through bankruptcy proceedings in London. He was involved in all the early manoeuvering to set up a 'proper' government, and ended up as the Resident Magistrate for Wellington for 20 years, always referred to as plain Henry St. Hill without the James. He also had the largest horse racing stables in NZ of the time!
Alexander Turnbull/Timeframes has a photo of him, and he looks decidedly unlike what one might think a Resident Magistrate would look like — sort of small and a bit lacking in gravitas!
James Henry St. Hill 1807-1866His house was on Hawkestone St, (later called Old Karori Rd?), and can be seen in many early illustrations of Wellington. I say
his house, but his father (of the will) must have lived there too. The one 1861 death notice I've found for the father states, "at his residence Hawkestone-street ... Henry St Hill, Esq, aged 78 years."
It was a nice house!
Henry St. Hill's house, Hawkestone SstreetHis other children all seemed to do well; youngest son Colonel Windle Hill St. Hill became a member of the Tasmanian Assembly, and at least one daughter married into a titled family becoming
Lady Ogle. Some of their death notices would say, for example, son of Henry Charles St. Hill of Bradninch Manor, near Cullompton, Devon, which sounds a whole lot grander than Ordnance Storekeeper, and that got me curious too but I haven't cracked it yet. The ring on Henry's left hand could have been his proof of lineage, but why would he want it buried and not passed onto a son? Must have fallen out, or been the black sheep, or even disinherited ...
... and one of his great grandchildren married my third cousin once removed!

Thanks again and again
Koromo

Edited to update the above links