When i've played England before, i used the first 10 turns to capture the rebel settelements of Bordeaux, Rennes, and Bruges in the continent while attacking Dublin. i made an alliance with France initially by marrying their princess (constance) to my faction heir (rufus) during the first turn. when i runned out of rebels settelemts to capture, ive began my covert operations against the french. ive trained spies and assassins in rennes, i used the spy to enter the french castle of Angers, then used my assassins to sabotage their chapel and kill off their priests! eventually after several assassinations, the Pope excommunicated them! so the french territorities is up for the taking. the strategy relied heavily on lots of saving and reloading. also it is better to have an assassins' guild on rennes for better effect.

just my two cents