From National Rail website (same information on Southern’s website)
Sorry for the late notice but I have been waiting for several hours for Southern to confirm whether their stopping service from London Bridge to Coulsdon Town on Saturday and Caterham/Tattenham Corner on Sunday which should call at Honor Oak Park and Forest Hill will be operating or not as both their website and National Rail’s still show it is not known how Southern services are affected by the engineering work!
On one hand Southern have told me that the journey planners should be accurate in which case these services are running but then told me they could see there are bus replacement services Coulsdon Town - London Bridge and London Victoria - London Bridge. This makes no sense at all especially as there is no mention anywhere about engineering works affecting the London Bridge - Victoria service at all and London Overground are running their services which would normally run to West Croydon to Crystal Palace as well as the services that normally terminate at Crystal Palace so therefore the line from Sydenham to Crystal Palace isn’t affected.
If Southern do get back to me then I will update accordingly.