London Overground advised in their weekend travel information email they are unable to operate services between New Cross Gate and Crystal Palace/West Croydon and v.v. after 2300 from Monday to Thursday this week. Although Southern Railways do not currently show anything in their engineering work for the same nights if you check times from London Bridge to Forest Hill for tonight the 2311 service is the last one displaying which leaves New Cross at 2318. They also show the last southbound London Overground service leaving New Cross Gate will be the 2315 which for anyone connecting from the Jubilee line departs Canada Water at 2308.
The last northbound London Overground service from Forest Hill is shown as 2317 and the last Southern service to London Bridge as 2324.
I recommend anyone travelling to or from Forest Hill after 2300 this week to check National Railways website or on the night live departures!
According to TfL there will be rail replacement bus services between New Cross Gate and West Croydon calling at all stations!