There currently is one option to travel by night train from Penzance (United Kingdom) to London (United Kingdom), taking approximately 7 hours: Namely the Night Riviera Sleeper EB operated by Great Western Railway.
Great Western Railway (GWR) operates the Night Riviera, a sleeper train running six days a week between London Paddington and Penzance.
The Night Riviera offers airline-style seats and cabins. Seats are complimentary and can be booked like a regular ticket. Cabins require a separate reservation and are popular, so early booking is recommended. Cabin guests enjoy complimentary light breakfast on board.
Sleeper cabins are available as either single or twin options. Each cabin has a sink with shelf and bin, UK power sockets, USB ports, a wardrobe, and under-bunk storage. The bottom berth transforms into a sofa during the day. Breakfast is served in your cabin.
Showers are available at Paddington, Penzance and Truro, but only for passengers who have booked cabins.
Cats, dogs and other domestic pets are welcome on board. Up to two pets can travel in your cabin without an additional pet fare, though a cleaning fee per cabin applies. Dogs must be kept on a suitable lead, and other pets must travel in a rigid carrier. Pets must remain on the cabin floor and are not permitted to sleep on beds. Only recognised assistance dogs are allowed in the on-board lounge, and pets should not be exercised in corridors or aisles.