The history in that movie is atrociously inaccurate.
I actually wrote my masters thesis on Robert The Bruce and how his role was instrumental in obtaining Scottish Independence
A section of my thesis talked about the historical inaccuracy of all of the battles, but surprisingly the movie did get the jist of what happened.
A. William Wallace was a real person. An enigmatic person probably due to how history recorded his presence. He was a figure head as a patriot and hero probably much due to the fact he was captured and King Edward I.
B. King Edward I (Longshanks) was probably accurately portrayed in this movie, along with his son Edward II. Although history shows that Edward I did not kill his "son's Lover", england probalby would have been far better off if he did!
"Physically, Edward was an imposing man; at 6 foot 2 inches he towered over most of his contemporaries. He also had a reputation for a fierce temper, and he could be intimidating; one story tells of how the Dean of St Paul's, wishing to confront Edward over the high level of taxation in 1295, fell down and died once he was in the king's presence.[201]"
C. Robert the Bruce probably got the short end of the stick this movie, the guy was an absolute BADASS in history. During the battle of Bannockburn, Bruce was chronicled to have allegedly ran infront of his army w/ mace/axe in hand and on the back of a horse charged Sir Henry De Bohun and just outright slaying his ass infront of both armies as they stand conniving wimp, but I see how he had to be posed in the movie to help it meld well.
I have that old paper around here somewhere, it's like 25 pages long. I can't remember it very well