Not particularly useful but those signs are pretty useless anyway. They fail in that the requirement to bring to the attention of drivers the charge is in minuscule font. They also fail the CoP requirements on signage and as there is no entrance sign to the car park they fail on that point too.
However, as you are dealing with an IPC member, any all appeals will be exercises in futility. There's nothing to stop you appealing, if you are still in time to do so, but it is up to you if you can be bothered. Personally, I would just wait and see if/when they ever bother to issue a county court claim. That is ideally where you would have the best chance of getting this concluded.
It does mean, however, that you will just have to weather a storm of useless but threatening debt collector letters which you can safely ignore. If/when a LoC is received, come back for more advice.
I'm sure some others on here may advise differently. I would say get on with your life and see if the ever progress it further whilst ignoring all the debt recovery steaming pile of nonsense.
