Throughout the movie, we are told that Shelley and Sandra left Phil ten years ago, when Phil was in line for his third straight national championship. The current competition is Hair 2000 (and is sometimes called the championships of the year 2000, to confirm that isn't "just" a name), yet when his honors are announced near the end of the movie, we are told he was national champion in 1981 and 1982. For this to be true, Shelley and Sandra must have walked out on him seventeen years ago.
When Tony is first being shown the flip board (bought from Leeds Train Station) that lists all of the salons, The Cut Above is listed among the other salons, even though they had not even registered to compete at that point.
While the male audience members are lined up taking discs for the Men's Freestyle, it is first shown that the real model for Raymond's Hair Studio is number two in line right behind Hair Montage's volunteer. The camera cuts away from the line and we hear seven more models being called (including Raymond's "plant" who goes to the Style Warriors) before this man is called and directed to Raymond's Hair Studio.
Brian says that hair keeps on growing after you die. This is an urban legend that is not true, of which a cadaver barber ought to be well aware.