Hi Steve
first of all i ain't a mechanic but i have some working knowledge of them as a firefighter. once the internal belt mechanism has locked the only method to release it (without resorting to a belt cutter)is to allow the system to wind in more belt wile not under tension.
you could have a look to see if you could unbolt one of the points to give you some extra slack.
try fooling about with the front passengers belt so you can understand how it works, give it a sharp tug so it activates and then feel how much you have to feed back in to release it.
the other point to note is to ensure the car is level as this can also stop the mechanism releasing.
best of luck
Scott
scott
March 2007