Mark 3A coaches were deployed on West Coast Main Line expresses out of Euston to bring the three main long-distance routes from London up to the same standard.
Initial variants were Second Open (TSO) and First Open (FO).
Catering and sleeper vehicles continued to be Mark 1 stock until the introduction of Restaurant Buffet (RUB) vehicles in 1979-80 and the sleeper (SLEP) vehicles in 1981-82.
In 1988 the process was completed with the elimination of Mk 1 parcels vehicles and their replacement by Mk 3-derived Driving Van Trailers, making the WCML push-pull.

Scottish Region push-pull services were initially made up of four TSO and one FO Mark 3A coaches with a Mark 2F DBSO.
The FO was later converted to a Composite Open (CO) by the declassification of half a coach and installation of a partition between the two classes and an SO was removed.
These vehicles were removed from the Scottish regional routes in 1989 when they were replaced with Class 158 multiple units.

Chiltern Railways employs several rakes of Mark 3 carriages, hauled by Class 68 locomotives in push-pull configuration with Mark 3 Driving Van Trailers.
These mark 3 carriages have been extensively refurbished and modernised with the following enhancements:
Application of new Chiltern Railways Silver Mainline livery based on the former, defunct Wrexham and Shropshire livery of two tone silver
Automatic plug doors in place of the original slam doors (except for the two doors adjacent to the buffet car counter, which are no longer for public use)
Large doorway vestibule areas
Installation of economical controlled emission toilets with retention tanks
Retrimmed carpets in new trim
Retrimmed seats in new trim
New dado side panels and repainted wall end coverings
Power sockets at each seat
Improved ceiling mounted LED interior saloon lighting diffusers
The Driving Van Trailers have been modified with diesel generators to provide Electric Train Supply to the coaches when the locomotive is not running, such as when in terminus stations and when stabled.

Greater Anglia have refurbished their Mark 3 carriages, hauled by Class 90 locomotives in push-pull configuration with Mark 3 Driving Van Trailers.
These carriages have been refurbished with the following enhancements:
Application of new Greater Anglia livery – a white bodyside with black window surrounds and red highlighted doors
Installation of economical controlled emission toilets with retention tanks
Retrimmed carpets in new trim
Retrimmed seats in new trim
New dado side panels and repainted wall end coverings
An increase in Standard Class seating capacity by adding another eight seats to each TSO carriage, thus creating 80 seats per a TSO vehicle
Removing the kitchen equipment and 24 First Class seats in the former Restaurant Car vehicles, replacing them with 54 Standard Class seats
Power sockets at each seat
Improved ceiling mounted LED interior saloon lighting diffusers
Current coaches (2015) typically have 74 or 76 seats (80 seats on InterCity Anglia) in Standard Class to the 2+2 layout or 46 to 48 seats in First Class to the 2+1 layout.

Abellio Greater Anglia used a mix of eight, nine and ten coaches in their trains.
Mark 3A coaches were deployed on West Coast Main Line expresses out of Euston to bring the three main long-distance routes from London up to the same standard. Initial variants were Second Open (TSO) and First Open (FO). Catering and sleeper vehicles continued to be Mark 1 stock until the introduction of Restaurant Buffet (RUB) vehicles in 1979-80 and the sleeper (SLEP) vehicles in 1981-82. In 1988 the process was completed with the elimination of Mk 1 parcels vehicles and their replacement by Mk 3-derived Driving Van Trailers, making the WCML push-pull.
Scottish Region push-pull services were initially made up of four TSO and one FO Mark 3A coaches with a Mark 2F DBSO. The FO was later converted to a Composite Open (CO) by the declassification of half a coach and installation of a partition between the two classes and an SO was removed. These vehicles were removed from the Scottish regional routes in 1989 when they were replaced with Class 158 multiple units.
Chiltern Railways employs several rakes of Mark 3 carriages, hauled by Class 68 locomotives in push-pull configuration with Mark 3 Driving Van Trailers. These mark 3 carriages have been extensively refurbished and modernised with the following enhancements:
Application of new Chiltern Railways Silver Mainline livery based on the former, defunct Wrexham and Shropshire livery of two tone silver
Automatic plug doors in place of the original slam doors (except for the two doors adjacent to the buffet car counter, which are no longer for public use)
Large doorway vestibule areas
Installation of economical controlled emission toilets with retention tanks
Retrimmed carpets in new trim
Retrimmed seats in new trim
New dado side panels and repainted wall end coverings
Power sockets at each seat
Improved ceiling mounted LED interior saloon lighting diffusers
The Driving Van Trailers have been modified with diesel generators to provide Electric Train Supply to the coaches when the locomotive is not running, such as when in terminus stations and when stabled.
Greater Anglia have refurbished their Mark 3 carriages, hauled by Class 90 locomotives in push-pull configuration with Mark 3 Driving Van Trailers. These carriages have been refurbished with the following enhancements:
Application of new Greater Anglia livery – a white bodyside with black window surrounds and red highlighted doors
Installation of economical controlled emission toilets with retention tanks
Retrimmed carpets in new trim
Retrimmed seats in new trim
New dado side panels and repainted wall end coverings
An increase in Standard Class seating capacity by adding another eight seats to each TSO carriage, thus creating 80 seats per a TSO vehicle
Removing the kitchen equipment and 24 First Class seats in the former Restaurant Car vehicles, replacing them with 54 Standard Class seats
Power sockets at each seat
Improved ceiling mounted LED interior saloon lighting diffusers
Current coaches (2015) typically have 74 or 76 seats (80 seats on InterCity Anglia) in Standard Class to the 2+2 layout or 46 to 48 seats in First Class to the 2+1 layout.
Abellio Greater Anglia used a mix of eight, nine and ten coaches in their trains.
British Rail Mark 3