Engineering work is affecting First Great Western services between London Paddington and Bristol Temple Meads and Wales. An hourly service is running.
Trains are diverted via Oxford won't call at Reading or Didcot. There are buses between Swindon and Reading.
The London Paddington to Cheltenham service is also affected. Trains are only running to and from Didcot. Passengers for London should change at Oxford.
More top news
The sisters of a shop worker stabbed to death outside a party in Gloucester have appealed for anyone with information to come forward.
Find out which train services will be affected by the strike - and plan your bank holiday accordingly.
Bob Crampton has some good news about the weather over the coming days - he even uses the words "unbroken sunshine".