So - I received two parking fines for the same car park, the two overstays happened within a week of each other at a similar time of day.
I appealed the first notice, no joy, so paid it within the initial period - £60.
BUT I didn't even realise there was a second one, assumed the extra letters were reminders, until I get a letter saying the fine was now £100. Emailed to NCP explaining my error and appealing the fine.
In the meantime I get another letter saying it had been passed to debt recovery and was now £160! I have since written to them explaining the error, saying I would be willing to pay the £60 and that I don't think it's right to be penalised for the rise in the charge while waiting for more correspondence from NCP.
I really, really don't want to pay £160 for a 15 minute overstay in a car park, this doesn't seem fair. But the letters from debt recovery are all very official and serious and I don't want to keep receiving messages saying the fine is going up and/or I'm going to be taken to court 
What should I do?