All the London railway stations :
Underground lines : Northern, Victoria & Stockwell in google maps - the next station along the Northern line, at Morden, has a lift to street level, and lots of buses. The Victoria line also has better accessibility options, with Brixton being the closest accessible stations to Stockwell.
Accessibility friendly : You can change between Northern line southbound towards Morden (A step 183mm/gap 0mm) and Victoria line southbound towards Brixton (A step 50mm/gap 75mm). You can change between Northern line northbound towards Camden Town (A step 173mm/gap 0mm) and Victoria line northbound towards Tottenham Hale (A step 50mm/gap 75mm).
Stockwell is not accessible to wheelchair users due to escalators or 78 stairs between the platforms and street level.
Level interchange between Northern line northbound towards Kennington and Victoria line northbound towards Vauxhall. Level interchange between Northern line southbound towards Clapham South and Victoria line southbound towards Brixton.
General description :
More comment : Inclusive Britain Station Guide