WE Johns wrote Biggles books until his death (Johns, that is, Biggles never died...)
Here is a complete list of the Biggles books and a catalogue of what I have. My primary source for the list is Biggles.Info I have included a rarity score (4 stars is very rare) taken from this source. You might also like this Biggles forum.
I am mainly missing some of the later books that WE Johns wrote. In this catalogue, titles that are bold in this colour are ones that I don't have. Titles that are bold in this colour are ones I have only in Dutch or in the Bumper book. I have a few first editions also.
The first Biggles book I got was Biggles and Co. which my Dad brought home for me one day when I was about 12.
Many of the Biggles books are available in digital form. For example, fadedpage has lots of WE Johns books.