Rail passengers from the Uckfield area are warned of potential problems with journeys on Sunday, June 2.
Late-notice engineering work will close some of the lines between London Victoria and Clapham Junction.
On the Brighton Mainline, two trains per hour will run between Victoria and Brighton. One train per hour (stopping service) will run between Gatwick Airport and Brighton.
One train per hour will run between London Bridge and Oxted. Buses replace trains between Oxted and East Grinstead. The Uckfield to Oxted service will run to a normal Sunday timetable.
Metro services: London Bridge to East Croydon will be a normal Sunday timetable.