Search london history from Roman times to modern day
A bit out of date, but this interactive map of step free London is very good
All the London railway stations :
Underground lines : London Overground (Gospel Oak to Barking) and (North London line)
AccessAble Access Guide :
Accessibility friendly : No.
General description : See wiki
More comment : Step-free access between Platforms 2 and 3 only (TFL). British Rail Map & Guide - There are about 45 stairs down to the platforms.