Here's another map to complement the 'overcrowded bus routes' map that Michael posted. It shows the Tube lines that will run all night on Friday and Saturday nights from 2015.

http://www.tfl.gov.uk/assets/downloads/c...-map-2.jpg

As you can see, East London is well served by the Central Line and Jubilee Line, North London is well covered by the Northern Line, West London by the Piccadilly and Central Lines, of course.

Southeast London? Overground Line?