Southeastern operates a train from Folkestone to London hourly. Tickets cost $35 - $55 and the journey takes 54 min. Alternatively, National Express operates a bus from Folkestone to London 3 times a day. Tickets cost $10 - $15 and the journey takes 2 h 25 min.
From Folkestone Central train to St Pancras International. 54 min £31. From Folkestone, Bus Station bus to Elephant & Castle New Kent Rd. 2 h 25 min £10. From Folkestone Central Railway Station bus to Canterbury, Bus Station (Travel Shop) then bus to Elephant & Castle New Kent Rd. 3 h 13 min £14. From Folkestone drive to London. 1 h 22 min £13.