The first time I went to London we got everywhere by tube. I was shadowing the prof who taught travel study for our department. I realized toward the end of the trip that I had no concept at all of the city above ground. Your comment that most people who draw a London map most closely resembling the tube map does not surprise me. When I started teaching the class I made sure we got around by other means as well as the tube. I know they are touristy, but I think those hop on/off bus tours are great for getting a feel of any city above ground. I made sure to always do one of these for any city to which I took students when teaching the classes.