I found mention of the following videos, in Archery Talk, an online archery forum.These videos are on the Archery GB website, which is the official website for archery in Great Britain and Northern Ireland.
The videos are meant for coaches working with intermediate archers, but are really good for any motivated archer looking to improve, I found them to be clear, to the point and well illustrated. Find the link below:

http://www.archerygb.org/support/operations/coaches/coaching_videos.php