I have added many new videos recently to both the euphonium and the tuba video players on my site.
Below is a little pick-up group, including David Childs. This any many other new videos (including 7 by Steven Mead and 3 by Trevor Groom, who performs the Horovitz Concerto written for him), all available on the Euphonium Videos Page:
Here is one of the new videos from the Tuba Video Collection. It features some find playing by Steve Sykes: