ILS you asked how a professional experienced interviewer would spot a coached candidate. Easily, I have done it myself. Can I explain how? No, not really, I guess that if you are good at what you do, you can spot them... I guess you could call it aptitude!
You have not answered at least one of the questions posed here... how could anyone charge for a visit to a NATS unit?
Also - how much would this service cost? What are your (or your "friends") qualifications? Can you guarantee success? Can you measure added value?
I shall await your answers with interest