Billy Bunter's Own Annual.
Billy Bunter's Own appeared for the first time in 1953 and was last published in 1961. The annuals contained a number of short stories, mostly by Hamilton. You can find full details in the publications section of The Greyfriars Index
Jack Free in the Billy Bunter's Own Annual
One of the characters featured in Billy Bunter's Own was that of Jack Free, AKA Jack Nobody.
Jack Free stories also appeared in Tom Merry's Own
You can read an article by Derek Adley on Jack Free from the 1990 CDA here.
Hamilton also wrote 5 Jack Free books but only three were published. It is hoped that the two remaining books will be published some time in the near future.
Three short Jack Free stories appeared in the Billy Bunter's Own Annual, click on the links below to read or download.
Rio Kid in the Billy Bunter's Own Annual
Only one Rio Kid story appeared in Billy Bunter's Own, you can read it here.
The Rio Kid also made an appearance in the Popular, Ranger, Modern Boy, Boys Friend Library, Billy Bunter's Own and Tom Merry's Own.