Process worked great for me right up until the point I inserted the ticket to leave the car park, still within my prepaid period. At that point a message came up on the screen advising I had an additional £85 to pay! at 10.30pm on a Friday night after 8 hours travelling this is not what you want. To be fair, once I hit the call button and explianed the situation, the young lady on the other end managed to override the system and raise the barrier within a couple of minutes (she had all the deatils on screen I suppose). However, not a great introduction to using the "Priority" parking.