OK.
I finally got around to asking the local Mister Minit about our key.
They can replicate the key and it's transponder, so it will start the car. But they can't replicate the Remote Locking Unit.
So you can get a spare key which will start the car but needs to be used in the door to lock/unlock the car.
As an alternative to the massive dollar figures quoted here from Hyundai, it sounds OK to me.
$189.00
But I've found you can always talk them into a 10% discount.
Better than getting something from overseas IMO.
As a spare, I could live without the central locking option.