Complex sentence: The original show ("How)" was produced by Southern Television from 1966 up until 1981 when the company lost its franchise to TVS, which was a regular fixture in the CITV schedules.
Split into simpler sentences: The original show- "How"-was produced by Southern Television from 1966 up until 1981 when the company lost its franchise to TVS. It was a regular fixture in the CITV schedules.