Found this Glad if any use to you.
"The distance people need to go to escape (the travel distance) should be as short as possible. The travel distance should be measured from the farthest point in a room to the door to a protected stairway or, if there is no protected stairway, to the final exit from the building.
• If there is only one escape route, the travel distance should not normally be more than 18 metres. This distance should be shorter (12 metres or less) in any parts of the premises where there is a high chance of a fire starting or spreading quickly. The distance can be longer (up to about 25 metres) where the chance of a fire starting or spreading quickly is very low.
• If there is more than one escape route, the travel distance should not normally be more than 45 metres (around 25 metres in areas where the risk of fire is high and about 60 metres in areas where the risk of fire is very low)."