Removing clamshell
 

This might be a stupid question but the garage who inspected my faulty roof said that the clamshell was "extremely stiff" am I right in thinking there is apparently some bolts you can remove to fully remove the clamshell? Or atleast allow it to move freely

it's a few clips on the brackets on both sides that connect the clamshell to the chassis.
but you might be better off explaining what the issue is with your top so someone might help diagnose and recommend a fix. The only way i could imagine a clamshell being "stiff" is not having any grease on the rails it travels on moving up and down, which you can easily fix by just opening half way up and cleaning and greasing the rails.