Here is the CAA's view of Safetycom. I think you'll find that they have a very simple view of the system.
4 SAFETYCOM
4.1 SAFETYCOM is not an air traffic service.
4.2 SAFETYCOM is made available to pilots flying in the vicinity of locations having no notified VHF ground radio frequency. It is available to assist pilots to avoid potential collisions between arriving and departing aircraft and should normally be used only to broadcast the pilot’s intentions.
4.3 SAFETYCOM shall only be used at locations having no notified ground radio frequency. If a frequency is notified for a location, it must be used even outside the notified operating hours, using the procedures and phraseology published in CAP 413 Radiotelephony Manual (Chapter 4, Section 6).
4.4 Transmissions shall be made on SAFETYCOM only when aircraft are below 2000 ft above aerodrome or location elevation or below 1000 ft above promulgated circuit height (if applicable). Transmissions shall be made only within 10 nm of the aerodrome or location of intended landing.
4.5 The frequency shall be used only to transmit information regarding the pilot’s intentions, and there should be no response from the ground, except where the pilotof an aircraft on the ground also needs to transmit his intentions.
Exceptionally, where the pilot of an aircraft on the ground has information critical to the safety of an aircraft in a condition of distress or urgency, the frequency may be used to transmit that information.
4.6 Use of the frequency by pilots operating in the vicinity of an aerodrome that has no frequency assigned for communications is recommended, although it should be noted that its use is not mandatory.
4.7 Pilots remain responsible for obtaining any clearance that may be necessary to enter controlled airspace etc.
4.8 SAFETYCOM is only available within UK airspace.