Visibility versus protection
You're not thinking about VISIBILITY versus PROTECTION issues when you build your brand...but you'd better do it from the start!
You're already overwhelmed by all you have to achieve when you're building you fashion ID, build your brand, create your very first collections. Why should you bother about design protection? Why not just let go?
As you're dedicated to designing for your niche market, you think nobody pays attention to what you are doing. THIS IS UNTRUE
Fashion is a huge business where famous brands seat in a dominant position at the top of fashion business' pyramid. Their lawyers are paid to protect their designs on the global market, but not only. They protect the brand ID as well against any kind of copy. This is the "correct" side of the coin. Of course, nobody doubts that they are right to protect their image, their brands and designs.
On the other side, they can use their "money/legal power" to cover up less "correct" activities of the same brand. You can find numerous claims of young fashion designers after they found that their ideas, their sketchbook, their collection have been copied by a famous brand. But they can't afford to go legal and spend ridiculous amounts of money against wealthy companies, "The law defends those who can afford to use it" (read more on Vogue Magazine here). As a result, almost no fashion designer is going legal against such threats.
Be prepared, it happens all the time! Even to me, some years ago after I just registered my own name (Anya Camau is a nickname), I had a famous brand going legal against me arguing that both our names were similar. How could I be a threat to such a brand, being a self-employed fashion designer, just because of a remotely similar name? It finally turned out that I had to change my name!
What can a young, moneyless fashion designer do to protect his designs?
Not that much in fact. You are building your fashion business thus you must be VISIBLE, not only to your local market but the more global you are visible, the easier it will be afterwards to grow your business. Don't think about going legal against these companies, they could break you down easily.
Just prepare yourself for
If you feel a fashion company has copied your design work, first gather any proof to secure your position. Be very careful to stay on safe ground because you can't afford to get a lier reputation. If you're not sure, just let go and go on working on your next fashion show. The good thing is that a collection lasts for only several months.
Now if you can demonstrate that your design work has been copied, even partially, use social media. Just state what has happened and keep to the facts, your followers will do the battle for you. They are your supporters and will do their best to make your misfortunate known everywhere, at no cost! Of course, you won't win the fight just like this, but you will gain more visibility while sending the message to the company (and to other companies) that they'd better think twice the next time their design department goes into copying your designs. This will bring you as much protection as you can get in the fashion world, which is a ferociously competitive world.
After all, it's a kind of reward to think that such a famous brand has got far enough to copy you, take it positively and keep on going.