I am confused by external doors that would be used in the case of fire. Are all external doors emergency doors or do they become so as soon as an illuminated exit sign is fitted to any potential door that leads to the outside?

All doors you are likely to have to pass through to evacuate a building, are fire escape doors, some will be fire resistant (FD30/60 or FD30s/FD60s doors) others standard doors. All routes out of the building will become fire escape routes, in a fire situation, the ones used daily and familiar to all the occupants do not need to be signed with fire exit signs but all alternative routes unfamiliar to the occupants need to be signed with fire exit signs.

All final external exit doors leading to a place of safety are emergency evacuation doors and those used as alternatively means of escape, (not in normal daily use) need to be signed with Fire Exit signs. Illuminated Fire Exit signs or emergency lights used to illuminate the signs are not required if standard exit signs can be seen in the event of a failure of the electric power supply.

Maintained illuminated exit boxes are only required in certain situations like cinemas, theatres and clubs where necessary normal lighting is extinguished during the time the premises are occupied.

Hi,
While I understand signage for a 'Fire Exit', if I have a locked external door and hence not in fact a Fire Exit, do I need to sign this as 'not a fire exit', or does the fact that it is not signed enough to show that is it not a suitable exit. Would a Fire Exit arrow pointing the correct direction by correct?
Many thanks,
Tony

Has your fire risk assessment decided that the locked final exit door, you speak of, is not required, or suitable for means of escape, before deciding what signage is required or not as the case may be.

Assuming the door in question is not required for means of escape then it doesn't require any signage and a Fire Exit arrow pointing the correct direction would be correct.