You have the car, you are not clamped and I know that the collection agencies wont do anything with things like this other than send you demands on their letterhead which I suspect are just printed and sent by the parking company and not an actual collections company.
They cant do anything to get that money from you unless you voluntarily pay it to them. Not like those scummy council owned carparks where you will come back to your car and find a stack of tickets on it for things that have nothing to do with a parked car like an expired warrant etc.
I would also hope that someone can grab some video of the pay machine before they fix it incase you end up needing it. Probably something for fair go, target or john campbell.