The chariots are like weakened elephant units. They are best for breaking formations due to the launching attribute of attack.

It's best to charge through the enemy rather than let them stay in melee. Best to follow up with cav but Brits don't have cav. Use infantry to follow up quickly to exploit the chaos. I've had practically insta routed enemy inf this way.

Get Barb merc cav any time you can when playing the Brits, Worth their weight in gold.