Hi Eileen,
Wondering if you already have the passenger list record for ship Athenic, which sailed from Southampton, arrived in Wellington on 25 Feb 1921 with a Mr H Miles (age33, naval officer), wife ( no initial, age 18), Master C (age 6) and Master M or N (age 1) on it. Record found in FamilySearch.org - origin NZ archives passenger lists.
A Henry J Miles married an Edith Duke in Portsmouth in 1920. And another Henry J Miles married a Ms Watson in Paddington, London in 1921 - FamilySearch.org records also. Edith Duke was born 1903 in Cumberland - see ancestry.com records.
If you are near Karori cemetery, where Henry James Miles is buried, you could ask if anyone else is buried in his grave too - maybe wife?
Cheers
Liz