I am wondering if an existing block of 4 self contained and a shop on ground floor,  can be legally sold off as separate leasehold apartments, in the event they don't have fire separation between the units. The flats are in good order and lease individually and looks suitable for being split up and sold without further works. 

They may well have fire separation, I don't know.  Is there any way or clues for determining if they have fire separation i.e. if the conversion was done not earlier than a certain date to meet building control requirements? 

Many thanks. 

Pre 1991 there is a larger chance the separation isn't sufficient, although regardless of age inspection is preferred to confirm.

If not fire separated then regardless of whether the two areas are owned by the same or different parties there remains a legal duty to mitigate the risk to relevant persons either by installing separation or providing detection to the shop linked to sounders in the flats.