Not exactly - that is, there is no specific classic fairy tale that it's based on, like Snow White and the Huntsnman, for example. It would be more true to say that it has created a new fairy tale out of the traditional fairy tale elements, using them in a new way.

The way it is set in Scotland and based on the idea of ancient Celtic kingdoms makes you think of the old Scottish and Irish legends, which aren't exactly fairy tales but have that kind of feel when you read them. And the format of the prince (or princess in this case) who has to grow up and marry for the good of the kingdom, is an old fairy tale idea. Then there is the idea of having to overcome the monster and save everyone, which exists in old cultures, and among English-speaking people is at least as old as the tale of Beowolf.

So you could call it a new fairy tale created out of an ancient, internationally recognised genre.