I dispute the idea that Foxes don't kill cats
I know of three, one was cornered in a greenhouse, one entered a friend's house through the open kitchen window, caused mayhem in the kitchen and took the Siamese cat, another young cat was found dead in the garden with a broken neck
I have had a Fox in my house in the early hours of the morning when I let my cat out for her morning wander
I assume it was after her food
Luckily she was unharmed

When she was much older a Fox came out of the bushes and chased her I happened to be there and it ran off but I never let her out on her own after that