In The Patriot:
The movie character of General Charles Cornwallis is based on the real-life Lt. General Charles Earl Cornwallis. Just as in the movie, General Cornwallis oversaw the British Army's operations in the Carolinas in 1780-81.
In the movie, General Cornwallis is portrayed as a bit older, in his 50's, than he really was. Cornwallis was in his early 40's during the American Revolution. He is also portrayed to be someone pompous. This may not have really been the case, since he endeared himself to his men by often being at the front lines in harm's way along side them, rather than hanging back and watching the battle from the safety of afar.
Although General Cornwallis was part of the force that captured Charleston. He was not present at the surrender and occupation, because he was in the backcountry carrying on support operation. Although, the scene of he and Colonel Tavington in Charleston is not dated and could have been set several days after the first occupation, when he was in the city receiving orders.
General Cornwallis was the commander at the Battle of Camden defeating Maj. General Horatio Gates as in the movie. He also found his efforts to move into North Carolina frustrated because of the various militia bands that continually harassed his supply lines and outposts. Cornwallis also never met in truce with any of the militia leaders as he does with Benjamin Martin.
Though Lt. Colonel Banastre Tarleton was unsuccessful in tracking down Francis Marion, he did succeed in surprising Thomas Sumter. As a result, there is no indication that there was as much tension between Cornwallis and Tarleton as is portrayed between Cornwallis and Colonel Tavington over Benjamin Martin's elusiveness. In fact, Cornwallis supported Tarleton even after Tarleton was routed by Brig. General Daniel Morgan at the Battle of Cowpens. They maintained a long friendship that only broke up many years later over conflicting personal memoirs (and you thought that was a 20th century problem).