Stronger English in Kingdoms: Britannia

The title is really a shorthand of what I want to do, and I'm wondering if anyone has any tips about how to make it happen.

The Kingdoms: Britannia campaign has a lot of potential but the English faction AI is simply too passive. Playing as the Welsh, Scots or Irish it is far too easy to roll back the English - they don't ever become a threat; they're simply a speedbump on your path to victory.

I'd like to play a campaign where the English act like the dominant force on the island and go on the offensive for a change. It seems like the campaign was designed for you to play *as* the English; it's actually harder to do that than to play as the Welsh, which seems bizarre and wrong.

Any ideas how I can tweak the English to become frightening and aggressive? They already have the most provinces, the biggest military... how can I kick-start them?