Both the UK and Australia have an unregulated nails industry so it's pretty much anything goes.
In Australia, you don't have to have any qualifications in nails BUT if you are going to teach it as a govt registered course, you have to have a basic teaching qualification (which is woeful but that's bureaucracy for you). That said, there are many people who teach nails without it.
Not having a qualification under your belt isn't necessarily a bad thing, though and it doesn't automatically mean that you lack knowledge - some of the courses I've attended under the tutelage of self taught instructors have been brilliant.
I guess it boils down to being a discerning learner, researching all you can and availing yourself of good teachers. As has been pointed out, this site harbours a goldmine of information...start digging!