In theory, this should be a cheaper, less time consuming parking option. At the normal entrance barrier to the car park, the car registration is scanned and matched against the booking. Consequently, the barrier should lift automatically. When exiting the car park, a similar process occurs to allow automatic exit. However, this did not work for me so I had to buzz for help...take a ticket....then visit the manned booth on exit. It wasn't an enormous hassle but did negate the benefit of convenience from pre-paying for parking. It was, however, about £7 cheaper than paying by ticket on the day