Looking at Award's website again, it does appear to be the case that the short story books (Popular Rewards), although divided into sets of six, are sold in bulk - 36 books to a carton according to the order form. And it seems that Award will only sell to bookshops, schools and libraries.
However, the "How to Buy" page states:
Most UK bookshops are able to order books from us and your order should be delivered to the shop within a few days.
It will help if you take a note of the exact title and ISBN (the International Standard Book Number – on the below each book image), so that the book shop can track down exactly the book you want.
So, does that mean that individual titles can be bought after all then (by bookshops for customers who have put in an order)? I'm confused.
Click on the link to see the website - perhaps it will make more sense to someone else than it does to me! What a lovely lot of Blytonia - but can it be bought or not?!
Blyton books published by Award
Anita