I just pulled 5 books off my shelf:

Thomas Keightley, The World Guide to Gnomes, Fairies, Elves, and Other Little People, Avenel Books 1978 reprint of 1880 book. has 150 pages on Britain and Celt of a 550 page book.

Padraic Colum, A Treasury of Irish Folklore, Crown Publishers, 1967 edition.

Charles Squire, Celtic Myths and Legends, Random House 1994

Proinsias MacCana, Celtic Mythology, Hamlyn, 1970

Marc Alexander, British Folklore, Crescent Books, 1982