Are you sure they're not Jackdaws? They are early risers and make a whole lot of clacking noise right outside our bedroom window, starting at 4am at the moment. I imagine they are hitting the window either because they are attacking their own reflections, or there's something good inside. Try hanging a cloth or garden fleece over the outside of the window when you're asleep, so there's no reflection.
In spite of getting woken up every morning long before I want to, I really like Jackdaws. I love the fact that they stay together in family groups all year and I love their bright intelligence. They can give a death stare sometimes, and they demolish the fat blocks we put out for small birds in a few hours, but we just hope that means they take fewer eggs and nestlings.
Crows are usually alone, and although rooks can be seen in groups they don't generally haunt human habitation.