Help me remember a book

[Zooeyzo]

In the 90s I used to read a book or possibly series about a group of children in Wales who were quite mysterious and had powers. I remember names like ion.
Nobody seems to remember it and I want to find them to read to my daughter.
Anybody know what I'm talking about?

The Jenny Nimmo ones maybe?

Thank you @EineReiseDurchDieZeit I'll have a look at the library for it and see if it jogs my memory.

Is it The Owl Service by Alan Garner?

A String in the Harp, Nancy Bond

Susan Cooper's The Dark is Rising?

How old is miss peregrines school whatever it was?

The snow spider series?

Silver on the Tree, the final one in the series, is set in Wales (others may be too) so sounds like a good guess

I think The Snow Soider too. The most recent tv adaptation was fab btw.

I think it must be the snow spider. I will go to the library and have a read. Thanks everyone.