Members of the RMT (Guards/Conductors) on Chiltern Railways will be on strike on Saturdays 10 and 17 October.
Chiltern includes the alternative route from London to Oxford, and the usual route from London to Stratford on Avon.
EDIT- There is little effect on service levels - https://www.chilternrailways.co.uk/industrialaction
BUT note that the entire Leamington to Stratford on Avon service is CANCELLED- you will have to route via Birmingham then West Midlands Trains or use the half hourly X18 bus (at own cost) from Leamington Spa station.
Services to Oxford will run as normal.