Bevan,I doubt that I will be using any trains - heritage, or National Rail - until a reliable Covid vaccine is available.
Not visited K&ESR since the 1990s, when I got there using an All Line Rover, plus bus from Ashford to Tenterden - and much enjoyed my visit.
All Line Rovers no longer considered as reasonable value for money, and worsened bus service from Ashford makes access much more difficult.
In non Covid times there's still an approximately hourly bus service from outside Ashford International station to Tenterden alternatively via the a28 (2) or Woodchurch (2a). There is also these days a generally half hourly service from Headcorn Station(12) hourly on Sundays. As Headcorn is only an hour from London Bridge this will be the quicker journey from London for many people now. Overall Tenterden probably has the best bus services it's had for many years. Obviously we have been battling to get back to the main line for 60 years as well!