Wheel chair friendly route from knockholt/Orpington stations to Wembley .

Morning all, a certain non playing Palace legend is going to Wembley next Saturday and I'm helping him get to Wembley so looking for a wheelchair friendly route to Wembley from either Orpington or knockholt station. Any help would be much appreciated :p.
Massive thanks to hdeagle who sorted tickets via Pam at box office.
Cheers Orp:p.