It's too late to appeal now. APCOA are benign when it comes to litigation. You will just have to weather the Debt Recovery Agents (DRA) who are powerless to do anything. Never, even communicate with a DRA. Ignore them.
APCOA do not do county court. In the extremely unlikely ever that you ever receive a Letter of Claim (LoC) for this, come back and we'll advise on how to deal with it.
We do not need to see or know about any DRA or reminder letters. Use them as kindling.