It was under the Southern Railway that a number of alterations took place. After being formed in 1923, the company was determined to electrify the ex-SE&CR suburban lines using the LSWR-inspired 660 Volts D.C. system. Orpington received third rail first, this being laid from Victoria and Holborn Viaduct via Bickley Junction in 1925 – it was subsequently extended up to Charing Cross in 1926. However, it was not until 1935 that the third rail was taken south to Tubs Hill, in conjunction with the electrification of the Bat & Ball branch. Scheduled electric services began running through to Sevenoaks on 6th January 1935, and to coincide with this, partial modernisation of the site occurred. A new footbridge was built in prefabricated concrete, closer to the station buildings, and this time was treated to a pitched roof, as were the stairs. The existing footbridge became part of a dedicated footpath, until its removal twelve years later. Weather protection for the passengers took a decided step forward: for the first time, the island platforms each received a platform canopy, these being to the SR’s then prevalent V-shaped design (identical examples had appeared at Sidcup during the same year). The ‘’down’’ side platform saw its platform canopy truncated on its northern side as a result of the new footbridge’s incursion. The canopy on the ‘’up’’ side experienced similar, but also received a SR-designed upward slanting extension to its immediate south. Both bay platforms were closed and the lines of these subsequently became sidings. Platforms were numbered 1 to 6 from west to east: electric services from both Charing Cross and Victoria via Orpington terminated at platform nos. 4, 5, and 6. During the works, the SR also altered the design of platform gas lamp, bringing the station in line with electrification’s ‘’modern image’’. Lastly, a pair of sidings appeared on the ‘’down’’ side, to the south of the platforms; these were electrified to accommodate terminating EMUs. The Sevenoaks electrification had seen third rail installed along no less than fifty track miles, at a cost of £½ million (£23,860,150 at 2006 prices).
The next set of changes did not occur until the British Railways era. The first course of action was the removal of the ‘’Tubs Hill’’ suffix, such occurring in 1950. Exactly twenty years after the SR erected a new footbridge, yet another such structure was brought into use to complement it. The latter, also of prefabricated construction, but lacking a roof, was a much smaller affair, and only bridged the gap over the single-track between platforms 5 and 6; it was located immediately south of the platform canopies. Platform lengthening occurred in 1957: prefabricated concrete extensions came into use at the platforms’ southern ends, to accept ten-vehicle train formations. Such lengthening of the platforms was also in connection with the February 1956-approved Kent Coast Electrification Scheme, and at this time, gas lamps gave way to concrete brackets supporting electric lights. On 12th June 1961, electric working begun between Charing Cross and Ramsgate, via Sevenoaks, Tonbridge, Ashford and Dover, but such services ran to the existing steam schedule. Re-signalling of the layout took place in 1962, with the installation of three and four-aspect colour lights in preparation for electric working. On 4th March of that year, a ‘’power box’’ opened within the apex of the junction with the Bat & Ball line, which saw both Saxby & Farmer signal cabins decommissioned - this was swiftly followed on 18th June by the commencement of the full accelerated electric timetable. Three years later, general goods facilities were withdrawn from the site, this formally occurring on 4th September 1965, but a couple of sidings remained in use for coal traffic, until this itself was stopped seven years later.
1975 and 1976 were bad years for this station, certainly as far as aesthetics were concerned. The majority of the station was subject to a rebuild, which saw the original clapboard station buildings on both sides demolished. The layout was rationalised to leave just the two island platforms and their associated 1935 canopies – both footbridges were abolished along with the side platform faces. Immediately south of the SR canopies, a corrugated metal and glass footbridge - fully enclosed and similar in design to the example which had earlier appeared at Dartford - came into use, complete with lifts. This was linked to a then new all-glass station building to the east of the platforms. Bus shelters appeared on both islands and the concrete bracket lampposts were replaced with round-post metal equivalents. Despite the rebuild, Sevenoaks remained as a ''signing on'' point for drivers until 1984. In 1993, the ‘’power box’’ at the Bat & Ball junction went out of use, the Ashford Panel taking over thereafter. This involved a number of track alterations: access to the Bat & Ball route was restricted at the London end of Sevenoaks' layout to those tracks serving platforms 3 and 4. Furthermore, the former ''up'' berthing siding to the south of the platforms was converted into a running line. Finally, in 1999, electronic indicator displays came into use on platforms, and ticket barriers were installed within the station building.
It has already been mentioned that, before the full Kent Coast Electrification timetable came into use on 18th June 1962 on the ex-SER main line, a number of electric services had commenced a year previously, running to existing steam timings. After the commencement of the full electric timetable, which included revised timings for an accelerated service, there was still one noticeable working left in existence from the former steam-hauled schedule. Early each morning from Monday to Friday inclusive, a ''3D'' Class 207 ''Oxted'' unit would form a service from Tunbridge Wells Central to Sevenoaks. The unit would first run as empty stock from Tunbridge Wells West, round the curve to Grove Junction, before entering the Central station. Although the short West to Central station leg was not advertised for passengers, it being classed as an empty stock movement, staff did not mind passengers embarking at the former to save walking the distance between the sites. The service connected with London-bound EPB units at Sevenoaks, and was a leftover of the former Tunbridge Wells West to Sevenoaks steam working, which formerly operated during the peak hours. After arrival, the Oxted unit would proceed back to Tonbridge, and then on to Eridge.
With thanks to Clive Standen for providing information for the above ''service oddities'', and to Peter Greenhow for providing additional information concerning the 1993 track alterations.