This film was produced and directed by Dave Sproxton of Aardman Animations,
who are based in Bristol, UK. It was a 1 hour film made at the 1988
Standard Class Nationals at the Bristol & Gloucestershire Gliding Club,
Nympsfield. I happen to know this because I did some of the air to air
filming with a fixed camera mounted on the fuselage of my LS3a.
I'm sure you could get a copy from Aardman - they have a website with
contact details:
http://www.aardman.com/about-us/contact/
I don't think the film is available in DVD, but I have an original VHS
copy.
Hope this helps.
Ian