Well, after leaving it in place for another week, came home to find it had been triggered a few times. It takes a series of 3 photographs (at 3 second intervals). The first set showed a small dot quite far away - think it's a rabbit but it's only because the dot moves in between pictures you can tell it's anything. One of the sets clearly showed two rabbits but the last set is the most intriguing:
The other two taken just after this don't show anything, but whatever it was has a long tail... I'm still not convinced it's a fox but will set it up a bit lower in the coming days to see if I can get some more pictures