vintage children

so my boyfriend and i are looking for a specific children’s book that he vaguely remembers…

we don’t have many details, and we’ve been scouring the internet for it for the past few hours.

the most information we have is:

it’s an older children’s book (+10 years), there was a blue fairy that died keeping crickets warm during the winter, one was named nettle, 

there was a wizard who decided to sneak into some place and got shrunk after that,

the fairies had left their home or something like that?

it might not have been fairies, though–that might be a possibility, though he feels they were fairies (he says they were as big as crickets in the story)

it’s one book, not a series.

like i said it’s not much but if you have any information on what this book could be, please message me?