The work will affect trains on March 1 and March 2.
We have compiled all the details on these works so that you can plan your journey this weekend.
Saturday and Sunday (March 1 and 2):
No Southern trains will run between Havant and Portsmouth Harbour, Fareham, and Southampton Central.
Replacement buses (operated by South Western Railway) will run between Havant and Portsmouth Harbour and between Havant and Fareham.
Trains will run between London Victoria and Bognor Regis, and between Brighton and Bognor Regis.
Passengers can use Southern tickets on South Western Railway trains between Fareham and Southampton Central.
Sunday (March 2):
Engineering work is taking place in the East Croydon area, closing some lines throughout the day.
Trains will run to an amended and reduced timetable between East Croydon and Purley.
Trains between London Victoria and Reigate will be amended to run between Reigate and Redhill only.
Passengers should use alternative Southern or Thameslink trains to travel between Redhill and London.
Trains to and from East Grinstead will only run between East Croydon and East Grinstead.
Fast services between London Bridge and Caterham and Tattenham Corner will not run.
Trains between London Bridge and East Croydon via Peckham Rye will be diverted to run via Norwood Junction and will not call at Streatham, Streatham Common, Norbury, Thornton Heath or Selhurst.
These trains will also be extended to run to and from Caterham / Tattenham Corner.
Engineering work is also taking place between Polegate, Eastbourne and Hastings, closing all lines.
Buses will replace trains between Polegate, Eastbourne and Hastings and Ore.
Train services will run between Hastings and Ashford International.
