You may just have a boss! Normally every flock has one but it depends on how nice the "leader" is. Maybe you could search some other threads for "Agressive hen" or something? I wouldn't expect a hen to hurt a human as apparently they thing that we're their protectors..
I worm/mite my chickens, and all the chickens/chicks/poultry I've ever had I have never vaccinated and they have been spot on? I live up north from you in Staffordshire so not too far, but I seriously would not be fussed if you look after them in a clean environment?
Also for the territorial...