Posted: 22/07/2012 at 09:27
Mulch with big stone chippings (big ones with sharp edges, not little gravelly stuff). They won't dig through it and eventually just don't come back at all.
Or, cocoa shell (but not good for dogs).
Prickle strips along the tops of fences, and occasional raljex or jeyes around the boundary is repellent to them too.
I've used all these and they work very well