That’s a response to your appeal, not the original PCN.
Smart often fails in its PCNs to be able to hold the registered keeper liable for the actions of the driver, provided the driver is not identified in the appeal. Without the original PCN and the text of the appeal, this avenue of defence is no longer available.
If you tell us that you identified the driver in your appeal, if you said “I did this” and “I did that” in it rather than “The driver did this” then we’ll forget about this angle.