Really sorry for you. I have made 2 'chickens loose' signs for the paths approaching my house. No traffic other than delivery men, but we've had dogs in, chasing the hens, so it says 'please keep you dog under control, thankyou'. I even added a smiley face, since it pays to be polite, I find!
You can put signs up without permission, as long as you take them down if someone complains. As I understand it, signs are a civic/planning issue in England. Like most things, no action will be taken unless someone complains to the appropriate authority. Of course, some people make a hobby out of doing just that, but not on every street in the land.