Sadly, the S4C was withdrawn on 13 February 2016.
The link below is current at 05.03.16 for the S4 timetable even though it includes times for the S4C.
The Stagecoach website includes a route planner.
Click here for Stagecoach Website and Route Planner:
Click for S4 timetable : services4andsc431stmay2015