All the London railway stations :
Underground lines : Central, National Rail Chiltern Railways
AccessAble Access Guide :
Accessibility friendly : West Ruislip is not accessible to wheelchair users due to stairs between the platforms and street level.
National rail - There is flat access to Platform 4 at the National Rail station. There is no flat access to Platform 3.
General description : See wiki
More comment : National Rail Map and guide
Inclusive Britain Station Guide