I'm sure that's true of any tourist area and their local customs. I'm part Irish myself. According to Wikipedia, the earliest known reference to the leprechaun appears in the medieval tale known as the Echtra Fergus mac Léti.
My point in bringing up leprechauns is humans have a rich history of interactions with non humans, and these are often in the form of a smallish being. What ever you what to call them, it's all the same thing. They are all some form of faerie, gnome, troll, sprite, etc. And they often play tricks on humans. Other Irish folklore includes the far darrig and clurichaun.
Yes, I think I agree about the "hidden" space they are existing in. I'm not sure they are aliens in spaceships. I think they look like aliens in spaceships. But before we believed in aliens and even knew what a space ship is, people reported beings and odd things in the sky. The reports haven't changed much, including the occasional abduction. Faeries used to abduct people as well. We just gave them a new name and appearance.
There is also a long history of the idea that they are from a "hidden" realm. Celtic traditions include places like Mag Mell, Emain Ablach, and the Tir na nóg.
Now compare that to other myths, such as the Djinn. The Arabic root JNN means "hidden, concealed". The Djinn are shape shifters, and often take on the form of a black dog or cat, but they also appear in human form. They are known to harass and play tricks on humans. We used to have a phantom black cat in the house where I grew up. Lots of people would see it.
The interesting thing is that the old myths say these creatures occupy a parallel world to ours. And this is becoming a common idea as to the origin of things like UFOs.
Now as far as there being something to these tales of beings and spaceships... I've seen strange creatures associated with a landed disk. Six other people were with me at the time. They didn't look like "grays", but aren't that uncommon either (small black hairy entities with large glowing green eyes). Two of my friends whom I am still in contact with also saw these beings (one was with me the first time, and another saw one a couple of years later). Another ex girlfriend also saw one. They were also always seen by a brook, and under a bridge, which sounds like the old troll tales.
One of these friends also had an encounter with a small gnome like creature with a long beard when he was younger. His young nephew also reported seeing a small man with a beard in the same house years later. The other friend had a string of encounters with a strange phantom black dog, and she also saw a glowing orange "orb" with her mom and a neighbor when she was younger. Lots of strange stuff!
So there seems to be something going on that is not much different from the old tales.
Of course these comparisons are not new, and Dr. Jacques Vallee pointed this out back in 1969 with his book Passport to Magonia, as well as Messengers of Deception.
One interesting thing I have been noticing is that different cultures have their own paranormal entities. My grandmother was from Ireland. My dad used to tell me stories of the Banshee. He said his mother used to hear it, and he did too when he was young. And he continued to know when people had died via a series of dreams. My friend mentioned above that was seeing the phantom dog, her mother was from Ireland, and once again, the Banshee seems to have followed her to the US. Then you have other localized phenomenon like el chupacabra, etc.
So it seems where ever you go, there are local legends with this odd stuff.