Okay, this theory was conceived before Reading Festival 2003 and modified afterwards. Here's the theory:
Billy loves Benji. (Just accept all these facts; none of my theories have any proof whatsoever.) However, Benji and Tony from Mest are in love and plan to announce it at Reading Festival 2003. The plan is, Benji will dedicate a song to Tony, whereupon Tony will rush out from the side and they will run away together. What the pair don't know is that Billy is so obsessed with Benji that if he finds out about him and Tony, he will leave GC and never return.
However, this plan is never executed, because evil people throw bottles at GC. Benji never gets to dedicate a song, and Tony has a phobia of plastic bottles so he won't come on stage. So, GC simply walk off stage, and Billy hasn't found out yet... Haha bottle-throwers, you have inadvertedly kept GC together!! Ahahahaha! Now Tony and Benji are gonna have to announce their love another time... Maybe on December 16th, at the GC/Mest gig! Bwahaha!