Advice:
-Use forests to your advantage. Flyers can't charge into woods.
-Stagger your battleline; a lot of players I see go for one solid battleline; I imagine that as the equivalent of putting all your pawns in a row. Rather, I would put half your units in front of the rest, in a diagonal of sorts, slowly advancing in formation. Should a unit break, the enemy cannot pursue without being flanked and killed next turn.
-Bring magic: Bretonnian magic has a tendency to get neglected beyond defensive purposes. Lucky for us, one cannot give Magic Resistance to Pegasus Knights. Got a 2d6 magic missile? Watch the fireworks fly. Don't forget to bring the Rod of Power of course to convert your many unused dispel dice into extra power dice (Note, exception to this rule applies if you're dealing with a Fay Enchantress build).