Everything you've asked deserves a completely different answer depending on what type of person you are.
I personally left school at 16, went to work for someone for 5 years or so and then started my own business. I now earn far more money than anyone I grew up with and worked with and if my annual salary never increases any more than inflation then I'll still earn more than 99% of the folk I grew up with that went to Uni and got degrees.......BUT........ I'm clearly a lot different from a lot of my friends........bigger ambitions, more drive and more capable.
I wish I'd had more actual business knowledge but you can learn this on your own from books and online. I still wouldn't change anything about the way I did things.
This isn't right for everyone though and I would say the majority of folk are best working for someone else.
I personally think you could do as many Uni degrees on business as you like but you'd still be clueless how the real world of business works until you start doing it.
Having said that I can't recommend sacking off Uni either as for you it may be a better option.
Its really great that you want to start your own business and you should at some point. Just from reading your posts you sound pretty green though. What you think seems really simple and sure of making money isn't. Myself and a lot of others well experienced in business probably wouldn't touch it. Most textiles are made in China also.
Only you will know what you need to do......you may go to Uni and it will be the best thing you ever did or you may look back at it as a mistake. The same if you start a business.
I think someone fresh out of school has a good chance of failing at business as there are many thngs you just can't even imagine at that age with that little experience. You may be lucky though and make it.
One thing for sure is you'll not get any money out of a bank without some serious money invested from yourself.
I don't necessarily think you should go to Uni but I also don't think you should start borrowing money from family to set up a business needing 200k or so fresh out of school. Get some experience running a smaller business or go work for a lingerie company and make the mistakes we all did in business when there isn't 200k of your families money riding on it.
Also at a young age you'll think you can live comfortably on a lot less money than you actually can. I remember when I thought 'if I can just get on to 20k per year I'll be laughing'. I'm now on around 100k per year and thinking 'if I could just get to 500k per year I'll be laughing'