I would suggest the British Armor museum at Bovington. They have sets of plans for armor on sale. I had purchased those for the Valentine and Mk VIb previously.
http://www.tankmuseum.org/
use the "Learning and Research" link then look for the librarian's email address and send and email requesting information.
Mike T.
Beware the hobby that eats. - Ben Franklin
Do not fear mistakes. You will know failure. Continue to reach out. - Ben Franklin
The U.S. Constitution doesn't guarantee happiness, only the pursuit of it. You have to catch up with it yourself. - Ben Franklin