 Five former Caledonian Sleeper vehicles, now owned by Eastern Rail Services, are on lease to Network Rail for use on their Ultrasonic Test Unit, having been fitted with blue-star 27-way through wiring to enable push-pull working.Following the withdrawal of many overnight sleeper services in the late-1980s, many Mark 3 SLEP sleeper carriages were obtained by heritage railways in order to provide sleeping accommodation for heritage staff and volunteers.In 2019, some of the former Caledonian Sleeper carriages were preserved.