For every occurrence of the word "fine" you can show me in your correspondence, I will give you £100. As already stated, you have not received any "fine". All you have received is a speculative invoice for an alleged breach of contract by the driver from an unregulated private parking company.
The debt recovery letter is sent by a debt collector who is powerless to actually do anything except to get the low-hanging fruit on the gullible tree to pay up out of ignorance and fear. You can safely ignore any debt recovery letter and we don't need to know about them.
As you are now past any appeal period, you are simply going to have to wait for them (NPM or their legal representative which will one of several possible but litigators) to send you a Letter of Claim (LoC). Come back when you receive an LoC and we can advise further on how to deal with it and not have to pay these scammers.
