Traffic Penalty Tribunal (TPT) — England outside London
TPT handles council PCN appeals outside Greater London — bus lanes, parking, and moving-traffic contraventions. Hearings can be on the papers, by telephone, by video or in person. Free to appeal and you do not need a solicitor.
London Tribunals — Greater London
London Tribunals (formerly the Parking and Traffic Appeals Service) handles PCN appeals from all 32 London boroughs and TfL. Same three hearing types, same free-to-appeal model.
POPLA / IAS — private operators only
POPLA (BPA operators) and IAS (IPC operators) handle private parking charge appeals. POPLA is free; an IAS standard appeal is free if registered within 28 days of the operator's refusal (a non-standard one costs £15). The biggest grounds at both are PoFA defects, signage, and code-of-practice breaches.