The roll hoops are just bolted in but are usually over tightened, the tubes are then distorted and not easy to remove. Nippymog is correct about Bunny doing this job some time ago, the info is here:

http://www.talkmorgan.com/ubbthreads.php/topics/532787/2

That looks like an interesting project, an early car by the look of it with a G56 air filter ....and a nitrous bottle! Have a close look at the chassis for cracks in the usual places.