we have been to the o2 twice - last time being last sunday - and have driven and parked there both times. I booked and paid �20 for car parking each time when booking tickets from ticketmaster. I believe you are able to go onto ticketmaster and just book the car park should you wish. Its ticketless parking and the car park barrier recognises your card on entry, its really simple and i would rather know my car is outside than worry of possibly missing my train home!