Further batches were built between 1958 and 1963, the majority being for the Kent Coast electrification project but seven units were built for the South Western Division. These latter units were rapidly deployed to the South Eastern Division and some others were assigned to the Central Division. The riding quality of early units with Mk3 or Mk4 trailer bogies proved to be poor and latter batches were built with their non powered bogies being of the Commonwealth type

From 1979 onwards, following an experimental prototype in 1975, the class underwent a mid-life refurbishment which involved a major rebuild. The guards/luggage compartment in each driving motor was replaced by second class saloon and the TSK converted to a second saloon.  The TCK was converted to a trailer brake composite (TBC) with a new guards compartment taking the position of two (out of three) previously second class compartments. Another obvious external difference on the production conversions was the substitution of hopper ventilators for the sliding type of the original Mk1 design. The opportunity was also taken to substitute Commonwealth bogies from withdrawn locomotive hauled coaches for the poor riding Mk3 and Mk4 trailer bogies on the earlier batches.

Introduction of new Networker class 465/466 and 365 EMUs on the Kent Coast lines resulted in surplus Cep units being placed into store, though following privatisation there has been a significant redeployment and reformation of Ceps and Beps. In 1997 South West Trains acquired 16 Ceps from store and also exchanged some Veps for Ceps with Connex SouthCentral in 1998. Withdrawn Cep trailers have found other uses, for instance in class 207 DEMU formations and Cep TSOs have also been used to convert SWT Bigs to Cigs by substituting them for the buffet car, largely as a result of the Big buffets having some traces of asbestos in their roof and a kitchen area that did not meet current food hygiene standards. This was not a problem affecting the Bep buffet cars as they had been upgraded and kitted out with stainless steel kitchens during their 1980s refurbishment. Connex, on the other hand, reduced the 4 car formation to 3-Cep on some units, a change that was accelerated in 1999 in order to improve the performance of the remaining Ceps so that they could keep pace when being diagrammed to work to a class 375 Electrostar schedule - a task they proved to be very capable of despite their age. There was no move by SWT to convert their Beps to Ceps, the Beps remained satisfactorily in traffic until replaced by the class 444 units. They did, in fact, have their buffet cars re-fitted with new microwaves and water heaters and were re-upholstered with the latest red SWT seating covering to the bar and lounge areas.

On Sunday, 27th April 2003, Hertfordshire Railtours ran their "The Cep Salute" railtour using a pair of 4-Cep units and covering virtually all the Kent routes where these saw service. The tour started from Victoria and then travelled by way of Nunhead, Lewisham, Parks Bridge Junction, Chislehurst, Swanley, Borough Green Down Loop, Maidstone East, Ashford International, Canterbury West, Minster and Deal to Dover Priory with photo stops at Asford and Canterbury West. Following a further photo stop at Dover the units reversed and proceeded via Deal, Ramsgate, Faversham and Sittingbourne to Sheerness-on-Sea for another photo stop and reversal and then continued via Western Junction, Gillingham (another reversal), Faversham, Canterbury East, Dover Priory again, with another photo stop, Folkestone Central, Sevington Loop, Ashford and Headcorn Up Goods Loop to Tonbridge. Reversing once more at Tonbridge the tour then went via Tunbridge Wells Central, Battle and Hastings to Ore for a final photo stop and reverse, then via Hastings, Battle, Tunbridge Wells Central, Tonbridge, Sevenoaks, Bat & Ball, Swanley, Shortlands Junction, Catford and Nunhead to London Victoria.