We have to pay it, don't we? The only thing that should be payable is the 14 days prior to you receiving their letter. See the link I posted.
It says this:
The technical route: check if your 'Notice to Keeper' is flawed
With private parking tickets it's the owner of the car, not the driver, who's liable. Therefore parking companies will often send a 'Notice to Keeper' to the owner of the car. This is a formal parking charge notice sent to the registered keeper of the vehicle.
You'll get this through the post for one of two reasons - either you were caught on camera (and never got a ticket on your windscreen), or there was a ticket on the windscreen and it hasn't been responded to or the owner hasn't been told.
There are specific rules around how Notices to Keepers should be sent and written. However sometimes companies get this wrong. If they have, it's often possible to appeal on a technicality.
This route comes from members of our forum who have a great deal of experience fighting unfair parking tickets, and campaigning to help others do so as well. Many say it's worked for them (though not with NCP operators or some smaller firms). Here's what to do:
Check if the Notice to Keeper follows the rules
^There's a long list of rules Notices to Keepers need to follow (eg, if the ticket wasn't initially given on your windscreen, it should arrive within 14 days of the alleged parking offence). Our forum has info on what these rules are or the legislation is here- check whether the firm's followed all the rules with your ticket.
Write to the parking firm flagging up the error^
If you've found the parking firm slipped up, it'll give you useful ammunition in your appeal. First write directly to the company (contact details should be on the ticket) and explain what they did wrong - forumites have suggested a template letter in the discussion thread.