Sorry to hear that Foxy is lurking about. This happened to us and I remember saying on here how weird it was that we could see lots of foxes playing in the fields but they never bothered our hens...I was told not to be complacent and the TAS peeps were right. 3 weeks ago a fox attack at 1pm killed 10 hens - broad daylight as our neighbour hammered his fence 15 ft away!
The farmer where we live had his lamping man round within half an hour of our phonecall - we currently have a fox trap baited with dead hens. Blardy fox won't get in it though

Do you have a dog or can you borrow one to wee/poo nearby?
I'm not sure that any of these remedies truly work but at least you feel you are doing something while you wait for the trapper/shooter. Also contact your local hunt to see if they can come and help.
As for if you come up against it, not a lot you can do! I've chased one up our hill in my pj's and it kept turning round to laugh at me (as did the neighbours) they are very sure of themselves and quite possibly urban foxes dumped in rural settings

Make sure you shut the hens in soon as you can and let them out only once its proper daylight to reduce the chances of attack.