Mark Goodacre has posted audio lectures of George Bradford Caird's lectures on NT Theology at Oxford from the years 1979 to 1982. The audio files are not labelled according to content, so you will have to click through to discover the topic for each lecture. But for the purposes of this blog, it appears that at least lectures 31-37 are on the book of Hebrews. Lecture 34 unfortunately only has a tiny clip and so that lecture appears to be entirely lost. I will eventually create a separate page for these lectures.
Caird was originally slated to write the "replacement" volume on Hebrews for the International Critical Commentary. Caird decided to write his New Testament Theology first, but unfortunately died before completing this project. Naturally, the commentary on Hebrews was never written. The ICC volume has since been assigned to Philip and Loveday Alexander. The publication date for the first volume appears to be sometime in the late fall.