Eamonn,
I enjoyed both the book "The Annapolis Book of Seamanship" and the videos. Here is a link to the Annapolis DVD Navigation video.
http://www.amazon.com/ANNAPOLIS-SAILBOAT-NAVIGATION/dp/B000LXH5G8/ref=sr_1_7/002-4107224-6708806?ie=UTF8&s=dvd&qid=1175621727&sr=1-7
USPS also has a course called "Chart Smart" that may work. Even better would be make copies of the SEAL Navigation practice exams and get the whole ship to pass it.
Good Luck!