Hi Elle, those fabrics are beautiful. Do do an OBW with the flowers - I did my first one (Kathryn persuaded me!), it was easy from the book. And it was a big flowered Asian fabric too
http://www.quiltingboard.com/t-24480-1.htm
The book should come with a health warning though cos they are very addictive! I've now done 8, with 9 and 10 on the wall, and fabrics for 3 more in the queue....
You said about putting the OBWs "on top" of the navy trellis - you wont need to do that as the triangles for the hexagons are joined together in strips. Would be lovely as the border though.