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A bit out of date, but this interactive map of step free London is very good
All the London railway stations :
Cambridge Heath is on London Overground, and is not accessible to wheelchair users due to steps between platforms and street level. See pictures and further accessible transport in London detail from links below.
National Rail : London Overground
AcessAble Access Guide :
Accessibility friendly : There are steps to both platforms, making this station inaccessible.
General description : See wiki
More comment : National Rail map & guide