Three Cheers, Secret Seven
One of the authors mentioned was Enid Blyton. While we do have several books by Enid Blyton (and she was a prolific writer) that belonged to my uncle when he was a child, we had none of the books in the Secret Seven series.
PaperBackSwap had a few Secret Seven titles listed so I chose a couple and requested them. Then I read Three Cheers, Secret Seven. The seven are a group of three girls and four boys who meet regularly to discuss (and enjoy) mysteries and adventures - a sort of detective/adventurer club - and to eat. (That's why Ms. Brocket featured them in her book.) One feast in this adventure included "...biscuits, of course, some rock buns, pieces of gingerbread, an enormous bar of nut chocolate, jam-tarts, two bottles of lemonade, and a bag of toffees." (Recipes for many of these are included in Cherry Cake and Ginger Beer.)
In this particular adventure, the Secret Seven launch a model airplane given as a gift to the sister of one of the members. The airplane lands on the grounds of an empty, closed up house - one behind walls and locked gates. Of course, the children have to retrieve the plane, but while doing so, one sees something that makes him believe that the house is occupied.
The children sleuth, and finally - sensibly - call in one child's father to help them out. They are able to solve the mystery and be of great help to someone in need.
I enjoyed the story, and I think my children will, too.