Here: www.honestjohn.co.uk/faq/private-parking-penalties/

Your POPLA appeal will fail on the facts because you paid £3 when you should have paid £3.20, and you will then be subject to the full charge of £100. Your only possibility of getting off is if the VAT element has not been correctly addressed, which depends on whether RPC parking is claiming damages (which are nit subject to VAT) or a parking charge (which is).