I never went for the ATC Flying Scholarship, but I have received 3 civilian ones for a multitude of flying under a similar process.
Show your passion for aviation, maybe you're teaching some of the first class subjects to cadets or helping out at your local airfield/local aviation events/AEF, aviation camps etc?
Link it to your current studies, position in ATC + future ambitions, how the scholarship would help you along the route to your chosen career (doesn't have to be pilot!) , how you'd look to continue flying after the scholarship has ended, it'd be good to know the background of the course (though I'm sure you probably do) and have a question or two for them perhaps.
Hope that helps a little bit, apply for as many scholarships as you can, not just the ATC ones, there are many out there that are often not mentioned to cadets, some offer full PPLs!