I visited Finsbury Park station in July 2019. It gets an accessible rating on the TFL map.
All the London railway stations :
Finsbury Park station
Finsbury Park is on the Piccadilly and Victoria underground lines and ThamesLink, and is now accessible to wheelchair travellers.
Step-free access stations have lifts or ramps - or a combination of both -
so that customers don't have to use escalators or stairs to move between the street and the platform.
January 2019 - Transport for London has announced the opening of lifts at Finsbury Park Tube station, the first milestone in a major upgrade of the station. The new lifts will provide step-free access to the Piccadilly and Victoria lines as well as to platforms in the Network Rail station, making it easier for customers with mobility needs, buggies or heavy luggage to use the Tube.
The project to upgrade Finsbury Park also delivers a new, larger entrance on the western part of the station which will create a new, alternative step-free route when completed. New ticket gates and a larger staircase have already been installed, making journeys quicker and more comfortable for customers using the station.
Finsbury Park platform is raised at certain sections to allow step free access to the train
Finsbury Park lift at platform level
Underground lines : Piccadilly, Victoria, ThamesLink
AccessAble Access Guide :
Accessibility friendly : Yes it is.
General description : See wiki
More comment : National Rail Guide & Maps