All the London railway stations :
I visited St Johns Wood street in July 2019. It has one long escalator to travel between the platform and the entrance.
Underground lines : Jubilee
St Johns Wood station
St Johns Wood escalator
Step free access between north and south platforms - I would recommend travel south, past Baker street
I cannot remember the step and gap onto the train
Accessibility friendly : St Johns Wood is not accessible to wheelchair users due to 100 stairs or escalators between the platforms and street level.
Escalator access between street and platform.
More comment : Inclusive Britain Station Guide