Hi Acton,
I took this 18 monthes ago and passed although I never took the actual job.
My role play was a scenario of being a conductor selling tickets on a late running train, customer has to get to an appointment, unsure what ticket to buy and unsure how to get to her destination.
The structured interview is three questions if I remember correctly, you are given them before hand on a sheet of paper and then you are given time to write down your scenario. Papers are then collected and one person at a time is called in, they then ask you to expand on what you have written before asking probing questions.
Are you in Watford for this?
Any more questions dont hesitate