Thanks to everyone for their help so far.
I've received another email from the paymyparkingcharge people saying that if I want to submit an appeal, to do it in the next seven days.
Is this a trap? As in an appeal rather than a challenge is some kind of acceptance?
I've obviously had a load of correspondence with them over the past few months based on the help I've had here, so I'm not clear what exactly I need to put in the appeal.
Any help would be really appreciated.