Hi Stamfordman,
Thanks a lot for your reply.
While I wait for Jack to give me details on the first two PCNs challenges:
- On the RingGo app: I selected a Permission to Park permit and after filling in my details, including my address, this is the permit the app / website selects for me:

CPZ L (34012) , which is in St. Pauls Road, whereas the entrance to the building is in Clephane Road, and the parking bay in front of it is on CPZ T, of which I don't know the location code, I assume 34018 on the basis of the notice of rejection.
Checking the council zone locator
here and using my postcode, it returns the same CPZ L zone as the RingGo app. To be clear, I do not understand why I cannot select the 'right' bay, and I was wondering whether those are reserved for residents of other buildings in front of ours.
- On the rejection offering: I assumed it was 65 each, but re-reading the wording now I understand I should have called them, as I could have considered to settle for a one single payment of 65.
I can also see that for the third PCNs there is no NTO delivered yet, I have not received a reply from my informal challenge yet, but it seem I can make the challenge again on the council website.