ceilidh = Scottish
ceili    = Irish

that's it simply- would suggest English dances be called something else and avoid spelling problems-barn dance or does that imply check shirts and spurs?- also suggest abolition of the much-abused term- 'craic'!!! enjoy the dance in Deal anyway.
My first visits to Scottish ceilidhs in the 60s were a surprise in that there was little if any dancing- I'm not a Gaelic speaker, and was told that the word actually means 'gathering' so there doesn't HAVE to be any dancing at all!