If you ‘overshoot’ and go all the way to the terminus of the coach line, you find yourself in Gloucester Green bus station. There is a taxi rank nearby. Walking is again an option (map on the left below).
There is an alternative walking route from college to department (map on the right below) – past the Natural History museum (of ‘dodo’ fame), Rhodes House, Keble College and along the University parks.
(Click on the maps to open google map webpages)