From TfL’s weekend travel information email:
Southern Railways are operating to/from London Bridge as follows:
Saturday
Forest Hill to London Bridge at 0558, 0628, 0643 and 0658 then at 13, 28, 43 and 58 minutes past each hour from 0713 to 2328 then 0001 and 0034
London Bridge to Forest Hill at 10, 27, 40 and 57 minutes past each hour from 0610 to 2357 then 0020 & 0035
Sunday
Forest Hill to London Bridge at 0749, 0805, 0818, 0831, 0848 then at 01,18, 31, 48 past each hour from 0901 until 1231 then 1246 then at 01, 16, 31 and 46 past each hour from 1301 until 2316 then 2347
London Bridge to Forest Hill at 0731, 0738, 0801 then at 08, 24, 38 and 54 past each hour from 0808 to 2254 then 2311, 2331 and 2350
Southbound services from Forest Hill on Saturday terminate at either Coulsdon Town or Victoria and on Sunday at Caterham & Tattenham Corner or Crystal Palace.