There isn’t any “limit”. It’s just a private company send the keeper an invoice for an alleged breach of contract by the driver.
There never is a “ interact in the first place. Why would you just pay someone because they say you owe them some money?
Don’t feel sorry for them. They make a fortune from the hundreds of thousands who pay the extortionate fee and the tens of thousands who get invoiced just as you did.
First of all THANK YOU for I found your advice incredibly helpful. My PCN was quickly cancelled. It is very unfair they take advantage of people this way.
Second, I would like to add a small, silly question: would the above apply to gatwick and stansted too? I'm asking not only for peace of mind but also because i have no way of knowing if the drop-off areas in these two airports work the same way as in luton.