The Assault Glider Trust at Shawbury may be able to help. They certainly have videos of many glider operations and exercises. I'm sure I've seen the snatch manoeuvre on Wacos on a video there.
I've got a (commercial I think) video from them called IIRC "Silently to War" or similar. Trouble is it's on VHS, and Teetering Towers is now only DVD/Hard Disc equipped. Must transfer it to DVD. O tempora, o mores.