Has anyone come across a situation whereby they have encountered unenclosed electrical meters and their associated electrical wiring in the common stairway enclosures serving domestic dwelling flats? If so would they consider enclosing such installations and why? The stairway enclosures in which the installations are located have no form of ventilation to fresh air.

Electric meter installations are quite a high fire risk ( I have dealt with many as a firefighter)and as common stairway enclosures should be very low fire risk then I believe the installation should be enclosed by fire risting cupboard.

You don't necessarily have to install a large ugly plasterboard and stud cupboard anymore either - there are products to allow a more compact and aesthetic fire safe enclosure:
https://envirograf.com/product/electrical-consumer-unit-and-distribution-board-fire-protection-system/

Thankyou Tom and Anthony for your replies. Appreciated to have other more informed views on this subject.

May I ask if this issue is mentioned in any guides, it is mentioned in 'Guide to making your small block....' I'm referring to low-rise 2 storey if there is anything available. Thank you.

You won't get much in guidance beyond "Rooms and cupboards containing electrical intake or electrical distribution equipment should have fire-resisting doors that are either kept locked or are self-closing" as it leaves the detail up to the Responsible Person and any external competent advisor - this could be anything from changing boards to metal, using a metal over sleeve, uprating existing construction with intumescent materials or lining boards up to complete new stud and board walls and new fire doors