Complex sentence: Ronseal is a British wood stain, paint and preservative manufacturer, responsible for the "Does exactly what it says on the tin" phrase, an advertising slogan created by agency HHCL which has since entered popular culture.
Split into simpler sentences: Ronseal is a British wood stain, paint and preservative manufacturer, known for the "Does exactly what it says on the tin" phrase. The advertising slogan was created by agency HHCL which has since entered popular culture.