The Chancellor's Building (Marked 'University' on this map) is accessed from inside the Royal Infirmary (Large blue arrows on map) - Enter by the West Entrance (revolving door) and turn left OR if entering from the East Entrance (bus stops and car parks) walk past Marks & Spencer / WH Smith all the way down to the West Entrance.
Images: LEFT - West entrance to Royal Infirmary RIGHT - Entrance to Chancellor's building (lecture theatre is just through these doors)