There was a case at London Tribunals on this exact subject, but I can't remember when exactly, which the appellant won. It hinges on the font acceptable for number plates. However, whether it was for a "1" instead of "I" or "0" instead of "O", I can't remember. The council are certainly being very venal here, (nothing new there !!), so if they have rejected your reps on this basis, you can take them with reasonable confidence to London Tribunals, but first can you please post up the PCNs then have refused to cancel, and ther rejection letters.
Sorry, but we do need to see the full facts of a case.