Hello Jan,
I have lots about Henri Garnay from Trove, Police Gazettes etc from 1881 until 1886, but nothing personal about his life.
In Gaol Description and Entrance Books Darlinghurst Gaol Nov 27 1886 there is a statement about him being returned to NC after being sentenced to 14 years' penal servitude. (attached) You might already have found this on Ancestry.
From State Records I have a copy of
Colonial Secretary, Main series of letters received, NRS 905:
List of former French convicts from New Caledonia residing in NSW, 1885 [4/887.1].
Henri is listed as Henry Chappin, liberé, tailor at Loise, Pitt Street.
Let me know if I can help. Cheers.
Lyn