Pre-booked parking, but on attempting to exit, the machine quoted some enormous sum, more than double the parking charge already paid. Middle of the night and dark and couldn't find the right button to call for help:- no light on the machine and for some reason there is a button to dispense tickets on the exit barrier, with the button for the intercom sited elsewhere on the machine. Having found the first one, not being able to read anything and there being no reason to think that an exit machine would have a button to dispense dispense tickets, it seemed reasonable to assume that pressing the button found would attract help. (There is just a picture of a finger pressing it on the machine.) Finally had to walk to the office, where people were watching screens but apparently not one showing someone in obvious difficulty at the exit barrier for several minutes. What are these people doing with their time? Why doesn't the system automatically tell them that someone has arrived at the barrier but has exited after the normal time? It really should not be hard to do this better.