Is that 250 kt.airspace by AIP so that controllers canīt let you exceed that limit even if they want to, of is it belonging to Prestwick making it possible for ATCOīs to approve higher speeds. Just a question from someone not familiar with the area.
Looking at your profile, why do you even care. Or is it just your profile thatīs not telling the whole story??
Do you think that 300 at 4000` is dangerous if no other traffic around?