Information needed please

[MummyG]

My son has received a notice prior to enforcement visit which he disputes on the day in question last summer he parked in a east Lindsey district council car park where he bought a valid ticket it was jammed packed and parked where he could on leaving the car park the attendant said that the ticket was invalid and for the car park next door to which he said he would give a parking ticket a few people questioned the attendent but he wasn't listening .just before Christmas he received a letter from Bristow and sutor then one after Christmas namely this one my son is disabled and this stress has made him have a pancreatic attack which can result with a hospital visit please could someone advise me as to what to do next thank you been told to pay arrears of 60.00 total ticket 158.00 .