You put the terms ie date time duration, services, location or incall and price you'd pay.
The service providers bid offers to you, some. If hit be more though.
You choose to accept one or not. If you do accept one that looks good, she will then not contact you, and you will have no booking, but analtwerp made two pounds. You will then complain and try again. History will repeat itself. Maybe two in 15 ( my stats in London) will be legitimate of the ones you accept.
Short version: save time, pay anusderp two pounds and nothing happens mostly.
Don't bother.