Anyone done Nightrider London (100 KM / 62 Miles)?

Myself and some friends are hoping to do this in June this year from Ally Pally. Has anyone out there done this before? Any tips for training or the ride itself? Were you able to use the toilet anywhere along the route?

I'm a totally new cyclist, hoping that I have enough time to train up for it. I'm going to use a turbo trainer to help me build up my fitness as well as doing outdoor rides when the weather improves and I feel that I'm fitter. I've read that you need to do a 40 mile ride at least 2 weeks before.