Recommended reading the terms and conditions of membership of the British Parking Association and the Security Industry Authority to check whether CES are fully compliant with the rules and regulations

CES state they are members of the British Parking Association who, on their site give a link to Security Industry Parking. I cannot see that CES have a licence to remove vehicles. I would think that if you were legally parked for example in your own car park and your space is designated in your lease, check the wording of the lease as I doubt there will be a requirement to display a permit. I would sue them for theft and extortion.