I think if you want to be a fashion buyer - a course in Business/Commerce with a side course in Fashion would be great.
I'm studying science and fashion and plan to do commerce aswell. That way I would have the research and analytical skills from my science degree (plus showing that I can do maths), then the creative flair, industry knowledge and forcasting skills from my fashion course and then general business skills from my commerce degree. Just an idea...
The best way and perhaps the only way for the inexperienced, is to start out by taking those assistant buyer jobs and working your way up and at least making some contacts out of it. Buying is one of those things that if you are good at it, you will be rewarded with better positions in a relatively short time frame. You will have to start somewhere - and as mentioned a lot of buying is actually sitting in an office looking at numbers and analysing them. Also a lot of research is involved too. The part most people desire is the travel and the collaboration with the suppliers. Remember that alot of this collaboration involves working with warehouses in Asia, not designers in Milan and that you might be buying 1400 etc of a plain t-shirt and not copulous amounts of frivolous dresses.