All the London railway stations :
Beckenham Junction is on ThamesLink network, and the whole station is step-free. There are also boarding ramps available. The tramlink at Beckenham Junction is exceptionally wheelchair friendly and accessible. See pictures and further accessible transport detail from links below.
National Rail : ThamesLink, London Tramlink
AccessAble Access Guide :
Accessibility friendly : Ticket office is step free. Platforms 1 & 2 are also step-free, for platforms 3 & 4 walk around station via a ramp. The London Tramlink is completely step-free.
General description : The London tram network runs from Wimbledon through Croydon
to Beckenham. All access to trams is step-free. All tram travel is free
for wheelchair users, who can easily wheel on and off the trams. There are two
dedicated spaces for wheelchair users to travel in each tram. Next to the wheelchair space
is a specially sited intercom, which allows you to speak to the driver in an
emergency, and an easy reach stop request button. All doors have an opening
button on them at an accessible height.
At Wimbledon Station there are passenger lifts providing connections to other rail services. See wiki