j2wo,
The policy is indeed 5 years employment history. Given you have none, I would assume that you've been at school for more than 5 years as you're 16. A letter from your tutor(s) detailing your where abouts in that period should suffice.
As Rainboe says, give them a call. They deal with these situations all the time and will have the answer to help you out!
Pass use is extremely limited and the access control system installed will not grant you access to an area which you are not permitted. That's not to say you can't go for a visit to the tower - you just can't rock up and say hello, anyone fancy a cuppa!!
Good luck with the job application.