Just thought I would mention this superb book on the natural history of the fox. Written by David Macdonald who did a groundbreaking PhD which exploded many myths about fox ecology, not least about what they ate. The best bits are published in "running with the fox" a good read and now it's a few years on it is very cheap second hand.
http://www.abebooks.co.uk/servlet/SearchResults?bt.x=0&bt.y=0&sortby=3&sts=t&tn=running+with+the+fox
http://www.abebooks.co.uk/servlet/SearchResults?bt.x=0&bt.y=0&sortby=3&sts=t&tn=running+with+the+fox