When I arrived at Farnborough in '74 and up to the late '70s, the system was:
FIS - Proximity hazard warnings; radar derived information could be used whether the aircraft you were providing service to was identified or not. (No SSR at Farnborough until 1981)
VMC Radar Advisory Service - On identification, the pilot advised you of his flight conditions and any subsequent change; the controller provided information on observed conflicting traffic but no avoiding action unless requested by the pilot or deemed necessary by the controller.
IMC Radar Advisory Service - as above but if the pilot said he was IMC, avoiding action would be passed by the controller followed by information about the conflicting traffic.
Procedural Service - non radar service to participating aircraft only.
Radar Control Service - provided for autonomous crossings of airways and applied before the aircraft entered controlled airspace until the aircraft had exited controlled airspace.
Late '70s (late '76 or '77 I think but I'm not sure) to 1980.
FIS - traffic requesting FIS was not identified and proximity hazards on other traffic were limited to other aircraft working the same ATC unit.
Radar Advisory Service.(RAS) - No requirement for the controller to know flight conditions; avoiding action against observed conflictions passed followed by any other known information about the traffic. This was later modified at the request of aircrew so that if the confliction was noticed with sufficient time, traffic information could be passed first followed by avoiding action thus enabling the pilot, if VMC, to look for the traffic and at his discretion decline avoiding action.
Procedural Service and Radar Control as above.
However, this did not allow sufficient flexibility for aircraft operating in MTAs (Military Training Areas) to carry out their programmed task without being vectored all over the sky so:
1980/'81
Traffic Information Service (TIS) was invented whereby, irrespective of Flight Conditions, the pilot would be passed traffic information but no avoiding action unless he requested an upgrade to RAS. TIS was intially only authorised for ATCRUs (miltary area radar units) and MOD(PE) units such as Boscombe Down, Farnborough and Bedford all 3 of which provided Area Radar services in addition to approach radar services.
1981 - 2009
TIS was re-named Radar Information Service (RIS) and authorised for all radar units providing service in the 'open FIR' now called Class G airspace.
With the widespread provision of SSR to airfield radar unts, it was recognised that FIS traffic could become 'known traffic' more easily so it was permitted to either identify FIS traffic using SSR or issue a 'conspicuity' squawk to such traffic; once identified and workload permitting FIS traffic could be passed 'generic' traffic information but not using the 'clock' code as this would be too similar to providing RIS.
RAS could only be provided to IFR traffic whether operating in IMC or VMC.
2009 -
You should know the rest.
Personally I preferred the 'original' system because it was easier to operate without SSR, the controller knew that if you passed traffic info under 'VMC RAS', the pilot had a good chance of seeing it and taking his own avoiding action and it meant that unlike if you were providing RIS or TS under the later systems, you could pass advisory avoiding action without asking the pilot if he/she would accept an upgrade to RAS/DS.
Bear in mind, I'm thinking back up to 55 years so some of my details and timescales may not be exactly correct.