I remember these units brand new at Penzance working a service to and from Cardiff, departing around 06.00hrs and returning late evening. This train was normally composed of 2 x 4 Car sets and a two car set, over the first few weeks I saw the complete class at Penzance. They had a miniature buffet in a four car set and rode on the then new Swindon B4 bogie. A very nice unit indeed.
Thanks Roger Winnen