have you got a dog at all? I'm not sure how TRUE this is but I was told that the scent of a dog can keep foxes away.
Wouldn't believe that- lost a hen out of our back garden last week- we have 2 dogs in and out of it all day
My chickens free range in the sense that they have access to a large area during the day however it is fenced with rentafence panels (we don't use the bases that you can get, the feet are pushed into the ground and then wood posts are put on the 'crease' where each panel ends and another begins)