The message
from "Geoff Bryant" contains these words:

Provided the leaf drop is not excessive it's normal. Griselinia leaves turn
yellow before the fall and can hang on at that stage for some time.

In the UK, griselinia only survives in mild coastal areas, where it's
evergreen. In the UK, it's not normal for it to turn yellow in June.

Are you saying it's deciduous when it's at home in NZ?

Incidentally, you may find it hard to imagine if you look at your plant, but
in the wild they often start life as epiphytes. Branch forks in the papery
bark of the tree fuchsia (Fuchsia excorticata) are popular sites for
germination.

Here (Isle of Arran, off west coast of Scotland) it often germinates
in the forks of trees, tops of old stumps etc, and I've seen it colonise
rock faces after seeding into the only other inhabitant, moss.

In the places where it grows on this island, it's a pernicious weed. At
Brodick Castle gardens we pull out millions every year, scarcely making
any impression :-(. But if it's in a situation where you can control it
by brute force (like my own garden), it makes a wonderful hedge.

Janet.