Not that the stop is particularly important if you've got the right fire seals, apart from stopping the leaf from crashing through the frame.
As Auntie LIn says and BS 8214:1990 gives a fuller explanation which is not contradicted by BS 8214:2008,
9.2 Single leaf, single swing, hinged doors
Single swing doors have doorstops, and it is widely recognized that door assemblies are often able to offer greater fire resistance when opening away from the direction of fire exposure. This has led to the erroneous belief that doorstops make an important contribution to fire resistance performance. Timber door leaves generally exhibit distortion due to shrinkage of the face towards the fire and the result is often seen as the edges and corners of the leaf tending to move towards the fire. Thus, if a door leaf opens in towards the fire the doorstop becomes irrelevant as the leaf distorts away from it. With a door leaf opening away from a fire the doorstop is on the exposed face and movement of the leaf edges or corners towards the fire is checked. This checking effect can be only temporary as eventually doorstops of any dimension will be charred away. When heat activated sealing systems are used, the doorstop makes no significant contribution to fire resistance. The size, type and fixing of the stop is, therefore, unimportant.
