These are not the usual "resident" foxes. They are considerably darker in colour.
As far as I can tell, there are three groups that visit. One group appears to have two adults and three cubs. Two of the cubs are almost identical, and the third is a bit smaller.
The other group, or groups, only seem to consist of a pair of adults. The foxes from different groups won't mingle together. Usually, one will run away immediately on sight of the "stranger".