Are you employed or self-employed? Have you been studying? All of these things will count as exercising Treaty Rights.
An application for Naturalisation is really easy! A lot easier than the altercations Dorothy came across on the yellow brick road! The UKBA want to see evidence that you have been here for 5 continuous years and have been exercising your Treaty Rights. So this will be payslips, bank statements, letters and transcripts from your university etc etc.
As easy as 1, 2, 3! Follow the yellow brick road! http://www.ukba.homeoffice.gov.uk/britishcitizenship/