Daxter

Hey guys, a few days ago I discovered this game and I have to say it's awesome! But I'm having a problem: I played against a pal of mine a few times. He always used the Britons and I tried different factions. Even though I'm superior to him in Economy and Military in the end screen I keep losing to him. After 20-30 minutes, after we built up our basic fortress, he runs at me with about 15-20 of his phase 2 cavalry and destroys everything. Mostly I tried to counter him with Roman spearmen, but he was even able to destroy about 30-40 of them with his few cavalry without getting significiant losses. Are there any good methods to counter this cavalry or are they a bit unbalanced at the moment??