We usually advise OPs to submit informal representations against the PCN, because sometimes the council manage to shoot themselves in the foot when rejecting those reps thus opening up more appeal arguments. You can, after that, wait for the Notice to Owner, sent to the name and address on the V5 Registration Certificate for the car, (is this you ?). This is beyond the discount period, so you would be taking some risk. Having said that, most London councils re-offer it because if they don't, it's a no-brainer for the PCN recipient to take them to London Tribunals, as the penalty doesn't increase. This means the council have the task of preparing an evidence pack which is a PITA for them.
If you lose at London Tribunals the full PCN amount is payable.
Please tell us why you parked there, because there are two exemptions to yellow lines, (1) loading, and (2) boarding passengers.