Hi, 

a little confused.

common entrance to 2 flats, recently converted.

both have FD30, with strips and self closers.

there’s x2 double plasterboard protection, ie 120 mins separation.

The hallway is 0.9m x 2m. 
 

Fire strategy report says no SD required in the hallway, but the FRA says we need a SD linked to both flats in case someone did an arson attack through the letter box!!

Seems a bit extreme, what’s right, what’s right wrong?

there no risk in the hallway, no fuse boards etc..

Any advice appreciated!!

Go with the fire strategy, the risk assessor is in a fantasy land. All that would happen with that alarm even if such an attack pccurred would be the residents would be drawn from the 1 hour + safety of their flat into a blazing hall.

A few years ago a pregnant women was killed by leaving the safety of their one hour compartment flat into a hallway that had been set ablaze with petrol purely because they heard an (unnecessary) common fire alarm go off. If there was no alarm and they had stayed put they would have lived.

I'd question the FRA in it's entirety if that's the level of it's content.

Anthony makes a good point. I do very little work in the domestic sector but I note that in HMO land this arrangement is often universal, at least here in NI. Usually mixed systems employed with 5839-1 in the common areas linked to AHDs behind flat doors and then a 5839-6 system in the flats. 
Care in opening a door in to a fire is a matter of education but even without ASDs in the common hall, the smell and sound of fire is likely to result in the occupants investigating anyway.