I've been reliably informed, by SIA, that the boarding pass for the onward flight will be in my sweaty palms as I wander down to Departures at AKL.
Having given my card details when I booked the room at the transit hotel, won't I get billed for it if I don't show up? Besides, a couple of hours in town, then back to the airport, into Departures and browse the area before retiring sounds good to me.

Thanks, once again, for all your help.