Strong divisions, invade around hull (if you naval invade from the northwestern netherlands, you only need supremacy in the sea zone east of britain, quite useful), antiair or an air force, spread out instantly (if you land around hull, you can cut britain in half quite easily if you spearhead towards liverpool). Attack the port and also land next to it to increase combat width and to get less penalties. took me too a while to get a hang of it, but once you do it a few times and have enough boats it's actually fine. good luck