I've heard about one or two MOT stations getting closed because of the following. VOSA are parking outside a garages, and using there laptops are able to see when a test has ended or begun. Using this procedure, when a test is finished they then pull over the vehicle has it leaves your station and inspect it.
Considering it has just left your MOT station there are no excuses for a bulb not working etc. Also if there waiting outside and see that you've just logged a car and none has entered the garage, they can then stroll in and ask to see the car in question, one of the garages nearby I believe was closed because of this, to save time they got the registration number and chassis number over the phone has the vehicle was on its way, VOSA walked in with the laptop and no car to be seen.
Remember if your building a new MOT station, get a underground exit tunnel built for your customers, wont ever have to worry again.