In all likelihood, you'll have to pay.
I went to POPLA with one last year as I could prove that the signage wasn't correct, but in a place like that and knowing PE I very much doubt they've got anything wrong. However, no harm in checking that the sign is visible and that the lettering is correct and reasonable, as that's the only get out you have. Please ignore anyone who tells you to ignore it, as they're very much wrong and since the Beavis judgement PE are actively taking people to court as they know they've got a slam dunk case now.
Personally, I'd pay up and move on. Life is too short.