The baseline safety rules are in JAR-25 which you can access online at
http://www.jaa.nl/jar/jar.html
For more detailed information I'd suggest two things:-
(1) Go to helitech at Duxford which is in a month or so, many firms trying to flog the technology will be there and you can spend a lot of time talking shop. (Gets you a free look around the Duxford museum as well, which is a bonus.)
(2) Ring up the librarian at the Royal Aeronautical Society, 4 Hamilton Place, London (0207-4993515) tell him what you're researching and arrange a day up there. He'll normally have all the current design textbooks and proceedings of conferences on the subject on a table waiting for you.
G