Complex sentence: The N91, is just the night replacement bus for the Piccadilly Line between Cockfosters & Holborn Stations and if you wanted to continue your journey you could take Night bus N97 to Hammersmith and Night Bus N9 to Heathrow Airport Central.
Split into simpler sentences: The N91, is just the night replacement bus for the Piccadilly Line between Cockfosters & Holborn Stations. Passengers can then continue their journey by taking Night bus N97 to Hammersmith and Night Bus N9 to Heathrow Airport Central.