SOLVED. Children's book with a magic portal, a character named Sebastian? [s]

[Lobstergirl, au gratin]

Extreme longshot...this would be a YA book that I read in the 70s. Probably pub. in the 60s or 70s, must be out of print now. The cover was purple and it was about kids who went through a magic portal - maybe a garden hedge, maybe a mirror? - to another world. I think there was a boy named Sebastian.

[Jackie "the Librarian"]

Lobstergirl, you may be looking for The Last of the Really Great Whangdoodles by Julie Andrews Edwards. It was first published in 1974.
Lindy, Tom, and Ben (Benjamin) go to Whangdoodleland through a hedge the first time they visit.

[Lobstergirl, au gratin]

No, it's not that one.

[Lobstergirl, au gratin]

I found it - so exciting! I've been trying to find this book for a year. It's this:

http://www.goodreads.com/book/show/29...

I wish I could find the cover from the early edition. It is now back in print. From an Amazon reviewer:

When Sebastian, a boy in Victorian England, sees an unhappy young girl in an antique mirror, he feels compelled to purchase it and free her from captivity. Melissa was kidnapped long ago by a wicked Enchanter who swore to deprive her adoptive father of whatever he loved most. Unless Sebastian can free her, she is doomed to spend eternity alone, trapped in the Enchanter's Treasure House, a place where time is meaningless.

To liberate Melissa, Sebastian must collect the Enchanter's five Power Objects---the mirror, a teapot, a silver fish, an emerald, and a green rose---and throw them into a magic well.

[Lisa]

Lobstergirl, Thanks for returning and letting us know!