It's still an F1 or F2 system regardless as to whether it is radio linked, cable linked or single station (although a system of unlinked alarms wouldn't now meet the BS5839 recommendations except where in conjunction with Note 1).
BS5839 says "In the case of Grade D and Grade F systems, where more than one smoke alarm is installed, the smoke alarms normally need to be interlinked" & "c) In all premises, all smoke alarms and heat alarms (if provided) in Grade D and Grade F systems should be interlinked, such that, when fire is detected by any smoke alarm or heat alarm, an audible fire alarm warning is given by all smoke alarms and heat alarms (if provided) in the premises.
NOTE 1 The above recommendation does not apply to smoke alarms or heat alarms in a mixed system (see 9.1.6) installed within an HMO if the smoke alarms and heat alarms are only intended to give a warning to occupants of the unit of accommodation in which fire occurs; under these circumstances only the smoke alarms and heat alarms (if provided) in that unit need be interlinked"
There is a section on wireless linked systems, only to clauses would apply to Grade F:
"If a radio‑linked system is installed in an HMO, all batteries used as the normal supply to manual call points and fire detectors should be capable of supplying the following loads for at least
5 years before warning of impending failure of the battery is given:
1) the quiescent load of fire detectors and manual call points;
2) the additional load resulting from routine weekly testing; and
3) the load from false alarms, each of 5 min duration, at the rate of two false alarms per smoke detector per annum."
&
"d) If the power supplies recommended in 15.4 and 15.5 are used to power radio‑links between smoke or heat alarms, this should not reduce the life or duration of a battery supply below those
recommended in 15.4 and 15.5 as appropriate."
If a single grade F alarm fails the others will operate individually once exposed to heat/smoke as appropriate, but the interlinking may not function as the 'chain' has been broken (depending how it's set up)
