A common strategy to consider is to ally Scotland and ferry troops into their border before the Maine event spawns. The Maine event fires quickly, so you may have to restart if you get unlucky.

Your troops, with Scotland, will crush the English army. You can take Welsh land and Pale (Ireland) in the initial peace deal, which opens the road to conquering the rest of the isles with ease.

Unallying Provence and attacking them when they invariably get excommunicated, as well as invading Brittany, are almost a must. You might be able to grab a few Burgundian lands, but the aggressive expansion is something to be wary of.

Aragon has some land you can grab, but I went to war with Denmark through a CB against Norway (after I ate Scotland) and grabbed low-development Swedish/Norwegian land.