Some countries extend copyright for 70 years after a creator's death, but some (prominent examples being Canada, and New Zealand) only extend it for 50 years.
Richmal Crompton died in 1969 and Thomas Henry, the illustrator for the vast majority of the books, died in 1962. So from January next year the Just William books will enter the public domain in the +50 year countries.
Canada has its own version of Project Gutenberg (Gutenberg.ca) and another site called Faded Page (fadedpage.com).
Volunteers on those sites are trying to digitize as much as possible because if the new trade deal goes through with the US, copyrights will probably be moved up to +70 years after death.
Faded Page seem scrupulous about getting the original texts and proofreading them thoroughly. If both the author and illustrator died more than 50 years ago they try to include the original illustrations as well.
Check out their early illustrated editions of some of Enid Blyton's work. Here is the first in the Malory Towers series.