Here is a link to Dinah Hall's review of The Liberators in The Sunday Telegraph. I would be interested to know whether anybody agrees with her - should children's books take place only in urban badlands? Why does the setting of a children's book seem to matter so much? Surely all levels of society / culture are suitable backdrops, as long as the story is good enough?
I remember when I was a child, I read The Family at One End Street, about a poor family whose mother took in washing. It never occurred to me that they were anything but children; in the same way, Just William wasn't middle class, he was just a boy, and the children in The House of Arden, who inherit a castle, didn't seem any different to me. Children don't think like adults - they have yet, fortunately, to gain all those horrible layers of social awareness that grown ups are burdened with. To a child, any child in a book is just another child having an adventure, and it doesn't matter what level of society they're on.
When you've clicked on the link, scroll down a little to find the review: BEST BOOKS FOR CHILDREN