Complex sentence: Edwards later said that their relationship hit the rocks following the death of his "Hollyoaks" co-star Laura Sadler, as shortly afterward his life headed in a downward spiral and he began drinking heavily, which greatly displeased Stevens.
Split into simpler sentences: Edwards later said that their relationship hit the rocks after co-star Laura Sadler's death. Shortly after Sadler's untimely death, Edwards' life headed in a downward spiral and he began drinking heavily, which greatly displeased Stevens.