From National Rail website:
As the London Bridge - East Croydon stopping service that Southern would normally operate is being rerouted via Peckham Rye and Selhurst there will be no services operating from Forest Hill / Honor Oak Park to or from East Croydon and this will reduce our services to London Bridge!
Our Sunday service will therefore be as follows:
Forest Hill to London Bridge
29 and 59 past each hour from 0759 to 2259
Forest Hill to all stations to Dalston Junction or Highbury & Islington
0648 then normal Sunday service from 0719
Forest Hill to West Croydon
Normal Sunday service from 0754 (0724 will not operate) to 2354
London Bridge to Forest Hill
28 and 58 past each hour from 0728 to 2258
Dalston Junction or Highbury & Islington to Forest Hill
Normal Sunday Service
West Croydon to Forest Hill
No service until 0818 then normal Sunday service until 2303
