The PCN is sat at £195 at the moment, keep an eye on
https://parkingpayments.lbbd.gov.uk/3sc/ and as soon as it goes up to £204, you can download
form PE3, print if off, fill it in (remember the applicant is the council, not you) and tick the box to say you never got the PCN, then make an appointment with your local county court or magistrates' court to get it sworn (this is free), or for £5 / £10 any local solicitor can witness you sign it.
Once that's done scan the form and email it to tec@justice.gov.uk with the PCN number in the subject line.
In theory you could wait for the paper copy to come in the post, but there's no reason to wait and there's no guarantees you won't have more postal problems, so you really don't want to rely on that.
When the amount due on the council website drops back down to £65, it means the PCN has been reissued. Let us know when this happens (you'll need to check once every 10 days or so after you've emailed TEC) and we'll help with a representation (again you should get a copy of the new PCN in the post, but you don't want to rely on that).
Any questions please ask.