The second batch was introduced in 1970 to replace 4-Cors on the Portsmouth Direct line. These and the later batch had detail differences to the 1964/5 batch with less comfortable seating. A third batch was introduced in 1971/72 to replace 4-Cors on Reading and Central Division services. Cigs and Bigs have never been allocated to the South Eastern Division.

In 1983, in order to provide sufficient catering stock whilst Big buffets were being overhauled, two temporary 8 Mig formations, sets 2601 and 2602, were put together as 4-Cig+RMB+3 Cig - note the use of a wired locomotive hauled catering car. Then to introduce the "Capital Coast Express" service for the summer 1993 timetable (prior to 319s becoming available) four 8-Dig formations (units 2001-4) were put together. These were semi-permanently coupled 4-Cig+4-Big sets. The Big was at the London end with the motor coaches as second and seventh in the formation. Inner set numbers were painted out but full yellow ends were retained within the sets and driving controls in the inner cabs were retained. The Digs were disbanded in January 1997.

Although the early part of the service life of these classes was unaffected by significant changes and refurbishment the past few years have been much different. Some 4-Big units have been converted to 4-Cig by withdrawing their buffet cars and substituting TSOLs from 4-Cep units downgraded to 3-Ceps. The difference in the window design between the refurbished Cep car and the original Cig/Big cars is very noticeable. Other 4-Bigs have been converted to 3-Cops ("corridor open-plan") by removing the buffet car and 1st class seating in the driving trailers. Compartment partitions were removed but the side corridor is retained and as a result the DTC is redesignated to DTSOL. One toilet is converted to a store in each DTSOL and a wheelchair seating compartment is installed in the former cage area of the brake van. These Cop units (originally classified class 424/3, but by 1999,class 421/7) were first used on Connex South Central coastway services (although they also strayed to London services on occasions) on 17th November 1997 and the full fleet was in service by February 1998. The improved acceleration is found to be an asset on these services. From mid 1998 CSC started the downgrading of 1st class accommodation in one DTC to DTSOL (as with the Cops), and by spring 1999 a wide yellow stripe on the roof was being added to identify the remaining 1st accommodation.

Before becoming 3-Cops these 4-Big units were simply renumbered into the 14xx series and ran for a short while with their buffet cars used as ordinary coaches.

SouthWest Trains eight created eight "Greyhound" units from redundant 4-Big units by replacing the buffet car with a spare 4-Cep trailer vehicle, which was identifiable by its different windows.

"Capital Coast Express" 8-Dig (Class 422/0, then 420)

These units were formed by Network SouthEast for the "Capital Coast Express" service which ran between Victoria and Brighton hourly, calling at East Croydon only, and were each formed from a 4 Cig and a 4-Big buffet unit. These units were classified as 8-Dig, or class 422/0 (but were, at some stage after 1995, re-classified from class 422/0 to 420). The units concerned were:

2001 formed from 1875 + 2262
2002 formed from 1716 + 2254
2003 formed from 1801 + 2255
2004 formed from 1715 + 2259

The 8-Digs continued to run for a short while without CCE markings when the Brighton expresses were taken over by class 319/2 units.