Never heard of any "court decision" obliging ParkingEye to cancel Lidl PCNs if a receipt is provided to show a purchase was made. However, as ParkingEye have a valuable contract with Lidl, they do not want to p!ss off Lidl by penalising their valued customers and so are very likely to cancel any appeal that can show the appellant was a paying customer of Lidl at the time of the alleged contravention.
Another reason why anyone who uses Lidl should download their app and scan the code at check out, even if paying cash. That way they automatically get an electronic copy of their receipt in the app.
Nothing worse on here than hearing about how someone was a customer of whatever store but paid cash and don't have receipt to prove it after they receive a PCN from the stores car park operator of choice.
