Hi, Chris,
You may be right, that K&C copied Airfix figures. It's up to Airfix to pursue it, if they hold the copyright.
The big issue is that there is a legal principle that someone who creates something has the right to profit from his creation, at least for a specific span of years. That encourages inventors, innovators, artists, etc, to produce and share their work with the rest of us. That's why we have patents, trademarks and copyrights. Brad (jazzeum) is more expert on the subject and can provide more details than this high-level description that I've given.
As far as we collectors are concerned, we can educate ourselves on spotting fakes, and decide whether to buy or not to buy a pirated piece.
But generally speaking, it's the holder of the patent, copyright, trademark, who has any kind of standing to pursue the pirate legally. I suspect that many don't bother. For a company like Airfix, they might decide that it's not worth the expense to pursue K&C. But a single artist, sculpting, casting and painting figures in his garage and selling them, might feel otherwise. Or he might be stuck, because the pirate has more resources behind him, and the artist can't afford to pursue it.
That's the big issue.
Prost!
Brad