It'll be SWR or any others that run in the south (not London)
So you should be fine with SWR
Previously day isn't strike
Saturday SWR are running an basic STP timetable, as they're are a lot of engineering works on the network
Check after 1700 the day before as any known cancellations will be uploaded once the resource team declare them around 1600
I expect Wey-Sou to be the wost as it normally is.
As I said before, any disruption or short notice sickness could have short notice cancellations
I'm aiming for London to south coast on 9th after holiday too and am relatively confident