It was a Slingsby Capstan. As you rightly say, a side by side two seater. I
believe some of the filming was done from the Cornish Gliding Club at
Perranporth, an airfield right by the sea cliffs.
http://members.aol.com/cornglide/page1.htm

"Guy Byars" wrote in message
...
I seem to recall a British program with a glider dropping cannon balls on a
boat full of bad guys. It had side by side seating, but I forget the type.
A Caproni perhaps.

Any of our friends across the pond remember this one?

Guy