London Paddington is not available and trains won’t run on the Greenford branch.
Long-distance services reduced to hourly and most will start/terminate at Reading.
However, North Cotswolds services will start/terminate at Slough instead.
South Western Railway will run every 15 minutes between Reading and London Waterloo from 09:00 to 19:00.
Trains between London Paddington and Cheltenham Spa will start/terminate at Swindon instead of London Paddington.
Trains between London Paddington and Bedwyn/Newbury will start/terminate at Reading instead of London Paddington.
Trains between Reading and Gatwick Airport/Redhill will start/terminate at Ash instead.
Trains between Reading and Swansea will run between Reading and Bristol Parkway and then restart from Bridgend.
Trains between Cardiff Central and Warminster will start/terminate at Bristol Parkway instead of Cardiff Central; buses will replace trains between Warminster and Southampton Central, where trains will run to/from Portsmouth Harbour.
Trains between Cardiff Central and Taunton will start/terminate at Bristol Temple Meads instead of Cardiff Central.
Rail replacement buses will operate between:
Maidenhead, Marlow and High Wycombe to connect with Chiltern Railways services to/from London Marylebone
Slough and Hillingdon for Metropolitan/Piccadilly line services, or Slough and Ealing Broadway for District/Central line services
Bristol Parkway and Bridgend (fast)
Bristol Parkway and Cardiff Central (fast)
Bristol Parkway and Newport (fast, plus calling at Patchway and Severn Tunnel Junction)
Newport, Cardiff Central and Bridgend
North Camp and Redhill (calling at all stations)
North Camp and Gatwick Airport (calling at Guildford only)
Warminster, Salisbury and Southampton Central
South Western Railway will run replacement buses between Andover and Gillingham – extending normal journey times between London Waterloo and Exeter St Davids.