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A bit out of date, but this interactive map of step free London is very good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 :
Bushey is on the London Overground, and is not accessible to wheelchair users due to there being 25 stairs between the street and the platforms. See pictures and further accessible transport in London detail from links below.
Underground lines : London Overground (Watford DC Line)
Accessibility friendly : No.
General description : See wiki
More comment : National Rail Map & Guide, 25 steps to platforms.