If the mediator says they are not legally trained, or refuses to say:“Thank you. In that case I’ll simply rely on my filed defence. For settlement purposes my position is that liability is denied and my offer is £0, or the claimant can discontinue with no order as to costs. I don’t wish to go into the legal arguments in detail; that is a matter for the trial judge.”
If the mediator says they are legally trained:“Thank you. I appreciate that, but I am not here to debate the legal merits with you. I will explain my case to the judge if it goes to a hearing. For settlement purposes my position is that liability is denied and my offer is £0, or the claimant can discontinue with no order as to costs. I’d be grateful if you could relay that.”
If the mediator starts probing the defence or expressing opinions on its strength:“May I ask in what capacity you are raising that – as a neutral mediator or as a legal adviser to one of the parties? I do not expect legal opinions from the mediator. I will rely on my filed defence and I will set out my arguments to the judge. For today, my settlement position is that liability is denied and my offer is £0, or the claimant can discontinue with no order as to costs.”
As for your second question about tiny “tariff level”. if the claimant offers to settle for the original parking tariff or some nominal amount, you have a straight choice: principle versus guaranteed closure.
If you want closure and are not absolutely wedded to principle:
"Without any admission of liability, I am prepared to pay £[tariff/nominal amount] in full and final settlement of all claims arising from this PCN and this court claim, on the basis that the claimant discontinues the claim and there is no order as to costs.”
If you are driven by principle and are comfortable going as far as a hearing (99.9% for sure will never happen):
“My position remains that liability is denied and my offer is £0, or the claimant can discontinue with no order as to costs.”
There is no hidden legal trap in accepting a trivial sum, provided the mediator records that it is without admission of liability, in full and final settlement, with the claim to be discontinued and no order as to costs. But it is entirely legitimate for you to refuse and stand on a £0 offer if that is your preference.
I have already explained that this will never get as far as a hearing and will be either struck out or discontinued if you let it run its course.