Am assuming it's a rat, but it doesn't quite look like the one or two other rats I've seen, and I know we get water voles in the area (there's a small stream at the bottom of the garden). From the state of it's tail, and the very hesitant way it moved up the garden, either way I'm guessing it's feeling a bit worse for wear.
I would agree with your initial thought in it being a rat as water voles ears are hidden and has a rounded face, furry tail and paws. Rats has visible pink ears, pointy face, pink tail and paws . It certainly looks like its been in the wars!