This is interesting. Thought I'd mention that in the mid 1990's the Angel tube station on the Northern line was redeveloped below ground, with platforms and track/tunnels being moved, and a new combined office block/station entrance replaced the original street level station with entrances about 100m from the original ones. I was lucky to be given a tour of the now-closed old station underground passageways and track sections - I took a lot of photos on 35mm film so I'll look them out, scan them and put them up somewhere.
Particularly interested in the Notting Hill photos as I used that station daily for 8 years, from 1987 - 1995.