I wouldn't personally, stick to the revelant facts on what would make you suitable for the role.
In every other job in the UK, people who are enthusiasts about the job they are applying for, would be seen as a good thing. This would always go in your favour. One example is programming. If you do not make out you are into computer programming as a hobby, it is actually a barrier to getting the job. Railways are the only exception. Railways are the only jobs where they want people who are not enthusiasts about the subject area that the job is in.
Not so in many cases. Whether or not someone gets the job is all down to how likeable the candidate is to the interviewers. If they like you and think you're capable of doing the job well, it won't matter if you tell them that you're an enthusiast.
As a manager I gave jobs to at least two gricers during interview, primarily because of the likely enthusiasm they would show for the job.
The problem today is dead-from-neck-upwards 'HR people' who have no personality or soul, who view candidates that deviate just slightly from the norm to likely be either a serial killer or a bankrobber.
I never seem to have a problem getting into railway/other roles and I've always mentioned that I have an interest in the industry in my CV, application and at interview.
However, I'm sure the way some people portray railway enthusiam in their applications probably conjures up images of the dribbling platform end spotters for some HR departments so it's no surprise they don't get anywhere!