Hi,

A fox will not take on a fit and healthy adult cat. The cat would win hands down.
They will however chance their luck with a less able cat...injured, old and infirm etc

We have foxes here too and the cheeky beggers think nothing of strolling round the streets in broad daylight
Initially I was majorly panicked by them especially when my youngest, who was only around 9 months at the time, was involved in a stand off with one in next doors garden
Since then I have seen him stalking the fox, not the other way around, and neighbours have told me that they were having a game of chase in their garden one day (playful chase) but I'm not sure whether I believe that or not