Male Urine has been tried and tested as a deterrant with some success here on GOY.

Going to the hair dressers and collecting lots of hair cuttings and putting some in each of a few old tights/stockings in the feet and dot them round your perimeter may well help . another thing that may help is to get a higher predetors droppings and put them round the edge will have a similar effect .

Try crumbled mothballs (naphalene) or old tea bags sprinkled with Obas oil in the areas where the foxes have marked out their territory.

Dried chilli flakes ( 99p. A small bag from ethnic aisle in supermarket) have deterred rabbits and squirrels, you could try it on foxes where you know they regularly go