I'm sure I heard a story a while back about some students in kent calling for an ambulance as part of a university study. Their friend prentended to be unwell and they hid in bushes across the road with a camera and microphone. I believe the ambulance crew figured them for the greasy scroungers that they were in about two seconds. I should imagine that said students can now be found working in a nearby fast food restaurant, staring whistfully out of the window...