I edited out my other post as it was for the wrong one of your PCNs.
Personally, I would not go down the unlawful declarationi route. If you do, it puts you at risk of a criminal prosecution and is certainly not supported by this forum.
Your household admin does seem to be a bit chaotic, sorry to have to say it, and it would seem you just ignored the PCN. If you did there is no second opportunity to submit reps now the Charge Certificate has been served. You could, of course, contact the council and explain things and ask them to cancel the CC and revert the matter to the PCN. You may strike lucky, you may not.