SIP/Gladstone -what do I do next?

In feb I got a letter saying I had parked somewhere and was issued a ticket (nothing to this effect) which I had not paid. The payment time had passed and now a higher fee was due. Contacted them immediately requesting evidence and informing I was never located there.They stated time to appeal passed and sent pic of a ticket on my car which couldn't prove the location. Wrote to IPC. They replied saying I would have to get SIP to accept the appeal process which SIP refused. Sent another letter to IAS requesting they look into the matter also contacted Citizen Advice. SIP sent letter of legal action. Refused to have any discussion on the phone and kept hanging up when i called. Later got a letter from Gladstone who claimed they were now acting on behalf of SIP and that a contract was formed just based on the fact that the signs were there and though no parking ticket was recvd I was committed to pay and that they were not instructed to litigate further.Responded that my communication was without prejudice aand that I am refusing liability.
I have since revised the claimed car park which is no longer owned by SIP so no signage evidence.
Since recvd county court letter to which I refuted the claim.
Gladstone wrote to me to ask for us to settle the matter of payment out of court. I refused. Since recvd letter from court saying they have assigned a hearing for which details are to follow.

question
1. is this where I prepare my defense even though I have retained all copies of letter sent?
2. what could my arguments of defense be other than the obvious of not being there - I am also a childminder and I would have been out collecting children from school in my own area of the time they are claiming?