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A bit out of date, but this interactive map of step free London is very good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 :
National Rail : ThamesLink
AccessAble Access Guide :
Accessibility friendly : Step-free level access via either side of station to each platform. Footbridge with steps between platforms. Alternative route via street - approx 500m with some steep gradients.
General description : See wiki
More comment : National Rail Map & Guide.