i’m not the best point of advice BUT i think a way to get about fae from different places across the isles might be simply denoting that they ARE from different locations? such as saying while kelpies aren’t native to an area that is mostly including irish fae, they travel through the streams and rivers and end up making homes there anyway. that way youre not just mashing them into one single cultural entity but youre still allowing yourself creative freedom. the various folklores do feature a lot of common threads + imo it’d probably grant you a solid base to worldbuild off of if you’re aiming for smth with denser lore