I have been to a purpose built block of flats which is 6 storeys high, each floor has 3 flats which has a communal lobby of less than 4m, the lobby is entered via a protected staircase through two sets of single fire doors.

The staircase does not have smoke vents however does have windows which can be manually opened, would this be deemed acceptable for an older purpose built block?

Many thanks in advance!

Quite possibly - the recently resurrected purpose built flat guide will help https://www.gov.uk/government/publications/fire-safety-in-purpose-built-blocks-of-flats

Thanks as always!