Never pay private parking companies
It's criminal. Basically, any private parking company can buy your details from the DVLA for £2.50 and then bombard the registered keeper with threatening letters, full of lies and intimidation.
This is despite any alleged contract being with the driver at the time, not necessarily the keeper, and the fact that these 'fines' are merely unenforceable invoices with no legal basis.
The DVLA will send you their standard template letter if you complain, in the same way these private companies send you a template 'appeal rejected' letter if you're silly enough to contact them.