Hi, David,
concerning the Messerschmitt works at Regensburg may I recommend this book:
http://www.amazon.de/Die-Messerschmi.../dp/3931904385
It contains numerous photographs about the building of the factory as well as drawings. Also contained are reports about the Obertraubling factory and the decentralized production around Regensburg after the big 1943/45 raids.
Regards
Roland