I don't think they have any intentions of building a platform 8 at Gatwick. I would have thought an island platform might have been useful. It appears there is just 1 platform for fast trains heading north from South of Gatwick, yet 2-3 in the opposite direction. For example trains heading south towards Haywards Heath seem to either use platform 5 or 7. Those heading north seem to use platform 4 only. May be some early morning ones use other platforms such as platform 3.