They have targets they have to meet to give you an appointment in 24hrs but you have to say its and emergency otherwise it doesn't fall into that statistic. mine always ask the question " is it an emergency?" I betting most do, my normal appointments are booked as I leave so if I'm ringing for one it's because I have an immediate problem, so always say yes and they will try and ask you about what the problem is and just refuse to discuss it with them. Then they just give you an appointment that day or the next, works for me every time but I usually get Mrs atm to ring for me as they wind me up so much
