Just be careful with taking foxes with your dog, if your dog goes off on the scent of a fox and kills it theres nothing you can do and the law reflects that so for that cub you were fine, but if it can be proved that you set out to deliberately take the fox with your dog (and I do know that its not easy to prove) then you would fall foul of the law.
Sorry if ive put a bad note to your thread, but wanted to make sure that you knew.
Beside that it sounds like you got a cracking little permission over there and keep up the rabbit control
Atb Ratty