Question Author
thanks for your answers :)
i have checked and there are definately no holes at all along the boarder... but the neighbours shed backs onto our shed so i think that the fox must be getting up and over there and that same route to get out, wildwood - i had no idea they could jump/climb that high!
will check online where i can get a ultrasonic detterant, jules77, cause i don't want to harm the fox but also don't want it in my garden, so i'll tyr this solution first... if it doesn't help we'll try the dogs :)
thanks again everyone, can't wait to see if it works for my fox.