Many aren't very detailed. I could do with more detail on e.g. King's Cross, a station where it's easy to be suckered into a much longer walk to / from your platform if you don't know some of the shortcuts.
King's Cross St. Pancras, for example, has 20+ pages of detailed 2D plans, covering the entrances, ticket halls, platforms, escalator areas, vent shafts and so on.