With respect to your query and the requirements of the national standard for electrical installations in buildings, BS7671 2018, there is nothing specific unless one was to accept that your installation fell within the scope of external influence BD2, BD3 or BD4 that relate to escape routes in defined conditions in which case regulation 422.2.2 would apply. This requires that the distribution equipment is housed in a non-combustible enclosure which is accessible only to authorised persons. There is nothing in 7671 that specifically requires the enclosure to have further resistance to the passage of smoke but the regulations that relate to installations within the scope of the above BD categories demand that cables and wiring systems have limited emissions such that light transmittance values are held within certain criteria. One can infer from this that vision within escape routes is of vital importance and as such any mitigation of smoke emissions from any part of the electrical installation specifically required or otherwise would be prudent if reasonably practicable.
I should point out that there is a general requirement enshrined in 421.1.1 that persons, livestock and property should be protected against the harmful effects of fire that may be generated or propagated in electrical installations.
