Anne Jackson writes
The message from K contains these words:

We lost all out earthworms a few years ago, when New Zealand flatworms
appeared over here. That was when I bought my wormery, and we're about
back to normal now...haven't seen a flatworm in last past couple of years.

UK earthworms had no difficulty in establishing themselves in NZ despite
the presumable presence of the flatworms, so it seems logical that your
earthworm population should have settled

UK earthworms, in NZ? Didn't NZ have its own worm population?

It did and still does.. But that didn't stop us inadvertently
introducing ours as well.

--
Kay