Debt collectors received for parking fine which is disputed

Nikkiboo

I received a debt collector's letter for a parkig fine - which increased the 'debt' to £170.  I parked in a private car park by Kripsy Kreme donuts but the store was closed.  I received a fine for being there 40 minutes - even though the limit is 90 mintues - on the basis that I am not a customer.  Although the signage says 'customer parking' it does not stipulate that the parking limits are different if the store is closed and does not give a definition of the word 'cusomter'.  I did not know that the store was closed until I tried to enter the store.
There is no definition of the word 'customer' and my point is that I am a customer therefore the 90 minute limit applies.  There was therefore no breach of the parking signs.
Should I respond to the debt collector? 

KeithP

It took you forty minutes from entering the car park to discover that the store was closed?

The fourth post of the NEWBIES thread explains exactly how to deal with debt collector's letters, but to summarise that post - ignore them.

Nikkiboo

Mechanical issues with the car, which is now no longer on the road as it died, but that's not the point - I was within the 90 minute time limit