Based on experience at Heathrow Terminal 5. Absolute disgrace and it's unbelievable that the management of Heathrow Car Parks allow this shambles of an organisation to operate on their premises. We ended up having to pay at the exit barrier because We Deal Meet And Greet had not validated the car park ticket that should have allowed us out. We phoned WDM&G at the barrier to sort out the situation. They didn't want to know, instead telling us that they only pay for one parking cost (i.e. when we drop the car off! Further phone calls were treated with contempt, abusive language and three times they hung up on me. After that I gave up. This lot are simply a fraud. Like many contributors to this website I heartily recommend you avoid these rip off merchants and make your car park booking with a bona fide organisation instead.