Cases like yours, (failure to update V5 promptly), appear time and time again on this forum, and frankly, because the situation is entirely of your own making, it will be very difficult, or even impossible to resolve satisfactorily. This is because the sole avenue to get back to the PCN stage is to submit an Out-of-Time Witness Statement, (one per PCN), to the Traffic Enforcement Centre that the PCN was not received. The only problem is that being out-of-time, the council are allowed to object to it and invariably do so, at which point TEC reject the WS. If your WSs are accepted, the matter will revert to the PCN stage at which point you can pay or submit representations.
You can, of course, contact the council, but will probably get the Bum's Rush, but try anyway. You would be requesting them not to object to your WS submission, and ask to just pay the PCN amount. Nothing ventured, nothing gained but you must realise you are in a bad place and there is no easy exit, I'm afraid.
Sorry if this isn't what you would like to hear, but it is necessary to be realistic. Please post up the documents you have received only redacting name and address.