If you like to play Russian roulette with your taxis, look no further. The process is familiar. Enter details online & receive a booking confirmation. At this point, your booking isn't actually confirmed though - you have to wait for a driver to be "allocated". If a driver isn't allocated, you are passed (transparently, without further notification) to other companies for them to pick up the fare. At this point, you have no idea whether anyone has picked up your fare, unless you go to their website and track your booking. Obviously I am writing this because I did this and found that no-one had, the day before I had to fly on business.