Does anyone here know anything about the Midsummer celebrations in England or Ireland? Also, if anyone knows anything about Irish fairy lore, that could be potentially helpful as well.
If you're talking about midsummer celebrations in the present, they're not around in the mainstream any more, in the UK at least. I don't know about Ireland, though.
On the other hand, if you're looking for past events, there's a few bits and pieces of info on Wikipedia. Here are the links:
fun fact i hear my evil twin once wrote a story about a hacker who used the name fyshi33k bc there are 33k-ish species of fish and she liked phishing so fyshi-33k made sense but then she got super embarrassed when someone forced her to explain — VyperShadow