After the fiasco of blowing up the bridge when Sharpe and Harper are waiting for debrief outside Wellesley's office, Sharpe refers to Wellesley as "Wellington". However, Sir Arthur Wellesley doesn't become the Duke of Wellington until the end of this episode.
Just after Simmerson gives the order to destroy the bridge, Leroy spurs his horse on. The horse at this point is a bay with a star, but when he canters down on the other side of the bridge he is riding a chestnut with a stripe
Sharpe teaches the South Essex to increase their rate of fire by simply dropping the musket ball down the barrel and tapping the butt on the ground to jolt it down, rather than using the ramrod. However, this method would only be used in an emergency as it badly affects the accuracy and power of the musket. It is perfectly possible to fire three to four rounds a minute using the ramrod, with practice. (Having said that, it is possible Sharpe taught them the shortcut because of the extremely limited time Simmerson allowed him to train them).
After the battle of Talavera, while the wounded are still being carried into the hospital, Countess Josephina informs Sharpe that London has created Wellesley Lord Wellington as a result of his victory. There is no way that London could have been informed of the results of the battle so quickly, let alone returned word of Wellesley's elevation.
The Battle of Talavera was fought in July 1809. Actors are frequently shown dressed for cold weather (heavy overcoats and such) and their breath is visible in several closeups, revealing that filming took place in cold weather.