Parking fines on private land - genuine mistake - any experiences?

[OhFreedom]

I've just had a large parking fine arrive, for a time when DH and I definitely attempted to pay (and thought it had gone through at the machine). We've checked our bank statements though, and can't find it, so the payment must have declined and we didn't notice, or something similar. Do I have to cough up? Anyone ever been able to explain and just pay the actual parking fee? It's such a ridiculous fine, for what would have cost about £1.50 in parking.
TIA.

If in England it's a charge not a fine and is enforceable.

There should be an appeals procedure on the paperwork so you could try that. But I wouldn't hold out much hope.

Thanks @VeniVidiWeeWee . It is in England. I don't think appealing will work (I've looked up grounds for appeal, and not making sure the money went through is not one of them!!). Parking companies are such utter fuckers.