In most cases, yes. Fire safety is covered by Part B of the Building Regulations, and an attic conversion usually requires a protected escape route. In practice this often means a fire door strategy along with mains-wired interlinked smoke alarms. The exact arrangement depends on the layout of your house, so it is worked out for each individual home rather than applied as a single fixed rule.
The purpose is straightforward. Adding a habitable room at the top of the house creates a new floor level, and the people sleeping there need a safe, protected way out if a fire starts below. Fire doors help contain a fire and keep the stairway usable long enough for everyone to get out, and interlinked smoke alarms make sure that a fire detected anywhere in the house alerts the whole household at once. These measures work together, which is why we talk about a fire door strategy rather than a single door.
This is not an optional extra or something you can leave out to save money. Part B applies whether or not planning permission was needed for your conversion, and it is a core reason an attic can be treated as a genuine habitable room rather than storage.
When we plan a conversion, fire safety is designed in from the start, not added at the end. You can read how we approach this in our process, and it applies equally to an attic bedroom. Meeting Part B also feeds into the Certificate of Compliance you receive on completion. To discuss what your home needs, arrange a free assessment.