The British are an economic based civilization but possess a strong military as well.
Early in the game they can create a large force of villagers since one is instantly created whenver a manor is constructed. As such extra villagers should be tasked to gather wood. This gives the British a small but distinct advantage in gathering resources early on. In terms of military the British have powerful force. Two mainline units, the Musketeer and Hussar, can be upgraded to Royal Guard. The British lack the Skirmisher, instead they use the Longbowman. This is a small disadvantage as Longbowmen cannot be upgraded past Veteran status. However the Home City can provide a card that allows Longbowmen to be upgraded further, negating this disadvantage. In addition their Home City provides many cards that improve the British navy, giving them a strong presence in water maps. The British army will likely consist of a large number of Musketeers with artillery. Due to the upgrades the British possess their Musketeers will be quite capable of countering any cavalry and most other infantry units while their Hussars can take out light infantry and artillery that can kill the Musketeers.
Despite the power of their military they do not possess any notable unique units. Both of their unique units are simply replacements of units that other civilizations possess. As such the British lack distinct combat advantages that many other civilizations possess. Artillery protected by anti-cavalry units will devastate British armies as the majority of their forces are composed of infantry.