CM069: National Grid Legal Separation - consequential changes to incorporate NGESO in STC Sections & Schedules

This proposal seeks to modify the System Operator Transmission Owner Code (STC) to reflect the creation of a new National Grid Electricity System Operator (NGESO) that is legally separated from National Grid Electricity Transmission Limited.  References to NGET have been replaced by NGESO, where relevant, throughout the STC Sections and Schedules in order to ensure the System Operator and Transmission Owner obligations are clear.