As a total amateur, but keen to learn, I have some concerns over all that is in this thread. I have read extensively on the dangers of cables over exits and exit routes falling down in a fire and causing obstruction to firefighters, but assumed this related to multiple cable types, power, lighting, alarm and data all being in conduit below ceiling height, assuming also that if these cables were above, say, plasterboard ceilings, then the problem didn't arise...at least not until the fire has such a hold that the ceilings collapse, either due to the fire alone, or due to a combination of that and, say, saturation from water from melted plastic water supply pipes. Then, if the cables are led through joists, is that safe, as it will take the fire longer to eat through the timber? If the cables are all clipped direct to the joists, or to rafters above, then the joists have to fail first, if the cables are on the side, not the top? Suppose you use metal clips screwed to the joists? The integrity of that would depend not only on the quality of the joists but also on the screws used to fasten the clips. A screw with 5mm mimimum penetration isn't going to hold as long as a screw with 50mm penetration...
Please note: I do not know the answer, but I am very interested on all views on this. I do have a view that suggests that in a single storey ground-floor building of modest dimensions, the exit time is likely to be so short, and the discovery of fire time equally so, that different considerations apply than for a multi-storey building with multiple occupants. The former is a much lower risk for firefighters entanglement than the latter, imho...is it not the case that there is no "one rule fits all" approach?