Well being an assistant to a 'fashion designer' and a stylist are two very different jobs, so might I suggest you narrow down you're dream first?
If you decide to be a stylist, there are two routes I guess. Assisting a stylist is always an obvious choice, though you would be doing many things and learning about the industry it's unlikely you'd be styling much yourself for a long time. If you can afford it do an internship at a magazine. You wouldn't get paid, but you would get to work personally on smaller projects and build up some tear sheets and learn about the industry. I know the fashion team at Arena magazine do this a lot, and I know a few stylists who've come from there by doing that. Remember tear sheets for your book are like gold dust at the start.
Education in styling is utterly irrelevant and you would more likely be laughed at for having a qualification in styling, I have never worked with a single stylist who has one.