Do you have a copy of Chapmans ?
They explain "Plotting" quite well.
I also received this publication when I attended a course given by the USCG Aux.
"Advanced Costal Navigation". Good reading !!
http://www.landfallnavigation.com/-bh029.html
The course was much more advanced than the OUPV requires.
Here is a link with most of the questions. Check the Merchant mariner Info Center.
http://www.uscg.mil/stcw/index.htm
FWIW....I found the Licensing "Schools" teach you how to pass the test but have limited time to teach the material.
Good luck !!!
I passed but it wasn't easy!.