So having read a lot more today. If I have sent an email to ZZPS stating I thought I had paid giving screenshots of the pay by phone receipts (at that point not realising I had used the wrong car park code) - have I not admitted being the driver? (Obviously I stopped communicating with them).
Also, looking through my emails I received a response from Bank about thinking I had paid and they replied:
This car park does accept the application as it is a nationwide app used by many parking companies and council however you have to pick the correct site code all our site codes begin with the number 8. You have paid the council and never paid to park in our car park on these occasions. As such the PCN’s were all issued correctly. Due to the timescale we are unfortunately unable to accept an appeal and the PCN’s are held with collections.
Obviously this does not show up when searching on the app, it only comes up with Cavendish street Code 2344 but underneath states Sheffield city council - on street. I think my only defence is they have not made it transparent that you can pay by the app and give the right code. The signage does not state any of this, hence the confusion and they also have a large sign saying Cavendish Street car park - which is why on the app I assumed this was the right one.