Clare at the Travel Centre said:
“I have checked the ticket for Julio: he is allowed to re-route for a charge of £50. Date changes are permitted free of charge so he just needs to contact Air New Zealand to make the change to routing.”
That would be the $75 you mentioned. I wouldn’t do anything yet just in case you want to do another re-routing. Your date changes don’t seem to have been free, though.
We watched Miss Marples 4.50 from Paddington last night. I then discovered it in book form on your shelves and started reading it, in order to understand more than the mere gist of what went on.