Are you sure it was the fox that killed your cat? Foxes are usually very timid and unless they have cubs (wrong time of the year) they will run away rather than attack. With regards to your chicken(s), human hair is supposed to deter foxes so have a chat with your local hairdresser and hang some in non plastic bags around the coop.
You may like to take a look at the National Fox Welfare Society website for info, it may make you change your mind as to how you feel about them. Personally, I love them and have a visitor every evening. As we build further and further into the countryside we are then in their territory, not necessarily them in ours. We feed them, our neighbour keeps chickens, result - one full fox, no attacked chickens.