National Rail Enquiries show the engineering works as taking place between Canonbury and Shadwell.
In addition on Sunday due to engineering works between Balham and West Croydon via Streatham Hill/Crystal Palace & Norwood Junction Southern are not operating the London Bridge to Crystal Palace via Forest Hill service.
This leaves us with only 2 Southern services an hour to/from London Bridge on both days. There will also be a rail replacement bus service X from New Cross Gate stopping at all London Overground stations including New Cross to Dalston Kingsland and v.v.
Forest Hill to London Bridge at 13,and 43 minutes past each hour from 0643 to 2313
There is also a connection through Norwood Junction at 0655 then 26 and 56 minutes past each hour from 0726 to 2256. Journey time is 23 minutes so only 6 minutes longer than direct services as it is non stop from Norwood Junction to London Bridge. However there are only 2 minutes to sprint between platforms at Norwood Junction!)
London Bridge to Forest Hill at 10 and 40 past each hour from 0610 to 2340 then 0020 & 0035
Forest Hill to London Bridge at 0749 then at 18 and 48 minutes past each hour from 0818 to 1218 then at 16 and 46 minutes past each hour from 1246 until 2346
London Bridge to Forest Hill at 0731, 0801 then at 24 and 54 past each hour from 0824 to 2254 then 2331 and 2351
Southbound services from Forest Hill on Saturday terminate at Coulsdon Town but on Sunday at Caterham/Tattenham Corner.