All the London railway stations :
Dalston Junction is on the Overground, and is accessible to wheelchair users between street level and platforms and trains. See pictures and further accessible transport in London detail from links below.
Underground lines : London Overground (East London line)
AccessAble Access Guide :
Accessibility friendly : Yes.
General description : Yes (TFL) See wiki
More comment : National Rail Map & Guide - Train doors stop level with the platform.