It's the same with all sporting events especially cycling ones. You get up early have breakfast, load the car, drive to the event. When you get there you need the toilet. So does everyone else they have all done exactly what you've done and the way the body works they all need to go at the same time.
I got this tip from Cyclosport's Howard Johnson just last year. What he does is he stops off at the service station before he gets to the event. Lots of parking and plenty of toilets.
JODRELL BANK CYCLOSPORTIVE 2011