It won't move that much, a little, maybe a mm or two. There are four torx head screws holding the rear glass to the rear mechanism. You should be able to see them from the inside just above the tracks. If you can crank it so it goes up, much easier but I don't think you have to. There are six holding the front glass to the front mechanism, same screws.

Good suggestion. However, be careful. These mechanisms are carefully balanced between each side. Any slight misalignment will cause the jamming to occur. Of course this could be the whole problem in the first place.Just a thought. cheers

Thanks guys. I only need a mm or so which means hopefully this sorts it out. I'll get back to you both when I've tried it.

cheers