I am in my 3rd year of Game Art Design at NUA(norwich) and have become very interested in mechanics design, e.g. how to moderate game flow, gameplay loops and how individual mechanics work in tandem with each other.

However I feel like this a very niche job and I was wondering what would be the best way of breaking into the industry with this kind of work in mind. 

There is no "one best way." There are a lot of ways you can get in. Any way that gets your foot in the door will enable you to work your way from whatever entry level job you have to doing the thing you're best suited for. I wrote an article for the IGDA about this very topic some years back: http://www.sloperama.com/advice/m85.html

For now, your best bet is to build an awesome portfolio, and to work on some student games and indie games as much as you can while you complete your studies (keeping in mind that your studies have to be #1 priority until graduation).

The thing is, it sounds like your asking about overall mechanics design. The high level or big picture design.

That is usually done by the lead game designer.

Mechanics are very foundational,and I'd think that is not really an entry level job.