Internal layout was for commuter services; low-backed, bus-style 2+2 seating in open saloons, wide gangways with hanging straps, and no lavatory facilities.

[7] Also introduced for the first time was rheostatic braking with cam-controlled analogue logic, and fluorescent lighting working at 50 Hz.

Interior design was open saloons with 2+2 seating, although this was not considered to be finalised until after trial running, and also included communicating doors between coaches and between units, with the driving cars having 2 pairs of sliding doors each and 3 pairs on the non-driving coaches.

[7] All three units were initially assigned to the South Western Division of the Southern Region, based at Wimbledon Park and Strawberry Hill.

In August 1973, all three units were moved to the South Eastern Division, where they worked services from Cannon Street/Charing Cross to Bromley North, Dartford and Sevenoaks.

It was also planned that the rolling stock for the services through the proposed Picc-Vic tunnel, intended as Class 316, would have formed part of the PEP family.

The PEP units had three sets of sliding doors on each of the non-driving cars for handling dense inner-suburban traffic.

However, the Class 313 and all subsequent builds, including later Mark 3-based units, have only had two sets of doors per car.