There is currently a major reduction in services due to geological problems on the line in the area of Yeovil. From Monday 11th August there will be a two-hourly service from Waterloo to Exeter, and a two-hourly service from Waterloo to Yeovil. (i.e. there's a train west of Yeovil once per two hours).
Correct current times are in on-line booking systems, and SWR have published a full timetable which can be viewed or downloaded here.
These changes are expected to last until some time in November.
More details here.
Not currently applicable:
You can view or download the current timetable here. The handy pocket timetable from SWR can be viewed or downloaded here.