During 1988, NSE was looking for a quick solution to replace much of the remaining slam-door stock which existed on those suburban Central Division diagrams operating to and from London Victoria. Although government finance was eventually agreed for the procurement of what later became the ‘Networker’’ fleet for the South Eastern lines, it was unlikely that the Treasury would submit to further monies being used in the meantime for more suburban stock renewals. Nevertheless, in 1989, British Rail was able to secure an order for an additional twenty-six Class 319 units for this purpose. However, to get the Ministry of Transport to agree to this batch, NSE masqueraded the order as an improvement of the Thameslink service, rather than as part of a suburban fleet replacement scheme. This final batch of units was delivered throughout 1990, and unlike earlier builds, these formations included First Class sections, which had been requested by passengers using the Thameslink service. Thus, stock reformations resulted in the First Class units being deployed on the longer Brighton/Gatwick to Bedford runs, which allowed existing Class 319 units with Standard Class seating to be cascaded onto suburban duties. This in turn made the withdrawal of older slam-door Mk 1 units feasible. The advent of the final batch of units created two subclasses: 319/0 and 319/1, these being Standard Class-only and with First Class seating respectively. The 319/0 series seated 319 passengers, but the 319/1 units had a reduced overall seating capacity of 272, sixteen of the seventy seats in the front of the Driving Trailer Composite Open (DTCO) being designated First Class. In 1994, those Class 319/0 units which had been cascaded to Central Division suburban duties became part of the EMU fleet of the then new Network SouthCentral (NSC) shadow franchise. During 1995, NSC considered removing the pantographs from these units, in addition to isolating the AC equipment, since the formations did not venture off third rail territory. However, the possibility of a service between Milton Keynes and Brighton came to light, which halted the alterations.
After privatisation of British Rail in 1996, more subclasses of the type began to appear and the units’ history hereafter becomes somewhat complicated. The fleet became split between two operating bodies: ‘’Connex South Central’’ and ‘’Thameslink’’. During 1994, the units had become the property of leasing company ‘’Porterbrook’’, and at 2000 prices, each Class 319 cost £306,000 per year to lease.
For the Summer timetable commencing in May 1993, NSE introduced the ‘’Capital Coast Express’’, running between Victoria and Brighton. For this, a fleet of what became ‘’8 Dig’’ formations were put together. One 8 Dig comprised a 4 Cig and a 4 Big unit coupled together, and there were four such formations created, utilising eight units. When the 1994-formed shadow franchise Network SouthCentral became Connex South Central (CSC) in 1996, the latter operating body sought to replace the Capital Coast Express and its 8 Dig fleet with a new premium service formed of refurbished Class 319/0 stock. Originally, the company had proposed calling the new Victoria to Brighton operation the ‘’Brighton Belle’’, but in light of the royalties associated with the name, the title was soon switched to the ‘’Connex Express’’. Consequently, Class 319 units Nos. 319014 to 319020 were selected for conversion to a new subclass, 319/2. This involved the insertion of eighteen First Class seats (in 2+1 formation) into one of the driving vehicles, in addition to a complete livery alteration. NSE ‘’toothpaste’’ colours gave way to pale grey and yellow vinyl, and inside, dark blue seating was joined with a carpeted floor. Since the fleet would be third rail-dedicated, the A.C. systems were isolated and the majority of the ‘’Express’’ units had their pantographs removed. The conversion work was undertaken at Wolverton. The Connex Express service commenced on 27th January 1997, and during peak hours, three Class 319/2 units would run in a single formation. Unlike the 8 Dig formations, no buffet vehicle was present, and instead a trolley service was operated. In light of the class not having end gangway connections, each unit within a single formation would have its own trolley service. The 8 Digs were consequently separated back into their erstwhile 4 Cig and 4 Big halves, and the units redeployed on the Central Division’s south coast lines between Brighton, Seaford, and Eastbourne. The Connex Express was the only passenger service not to stop at Gatwick Airport.