When the French cavalry charge the British squares, this is based on true fact. The French cavalry made devastatingly unsuccessful attacks on the British squares, though the number of times that they charged is still a heated debate.
In historical truth, the Prussians were indeed late to the battle, though that may have made all the difference. According to author Bernard Cornwell, if the Prussians had arrived on time, then Napoleon would most likely have backed out and would have fought another day. The way it happened, his army was far too involved to be pulled out, and Napoleon was utterly defeated.
Hagman's death is different in the novel than from the film. In the novel, Hagman is shot in the lung with the South Essex Regiment, and dies with Sharpe at his side. In the film version, he is shot in the head, outside the farmhouse.
Harry Price re-appears in the episode, alive, and played by a different actor. He last appeared in Sharpe's Company in Badajoz. He was shot by the evil Sgt. Hakeswill during an attempt to save Teresa, only Hakeswill got there first.
To save money and time in filming, separate events at the farms of Houguomont and La Haye Sainte were conflated in the film; thus the closing of the gates of Hougoumont - a critical moment in the Battle of Waterloo - takes place at La Haye Sainte instead.
The gray pelisse with the scalloped cape worn by an extra at the Cricket match is the same costume worn by Ann Firbank (Anne Elliot) in Bath in Persuasion (1971), an extra at the church at the end of Mansfield Park (1983), and by an extra in the London street in Sharpe's Justice (1997).