Complex sentence: The exception to this is the Fort William portion which consists of a First Class sleeper car and Standard Class sleeper car only-a Mark II Lounge Car and a Mark II seated carriage are added at Edinburgh for passengers joining the train there.
Split into simpler sentences: The exception to this is the Fort William portion which consists of a First Class sleeper car and Standard Class sleeper car only-a Mark II Lounge Car is added at Edinburgh. A Mark II seated carriage is also added at Edinburgh, for passengers joining the train there.