I am going to be making my daughters wedding cake in Feb next year and am currently practicing with recipes and techniques being very much an amateur. Ganaching under the ready to roll fondant seems to be the way to go but I have a couple of concerns.
1. I used chocolate melts with cream (live in NZ, these are cooking choc buttons by Nestle, v good taste) for my ganache which worked with the dark choc but with the white choc I felt it lacked flavour. Do I need to use very high cocoa content chocolate for my ganache? Also should it set to a cracking consistency, I rushed mine so it only sat for about 4 hours before applying the ready to roll fondant, was a bit gooey to eat I thought and just tasted fatty (sorry best way to describe taste!!)
2. Wedding is in Feb, Auckland is very humid then, hoping to get advice on timeplan for making and decorating cake and also keeping and transporting tips if poss.
At least I don't need to worry about the decorating, bunting around the sides to match the wedding colours and fresh flowers and ribbon to edge and top the cake, yay!! Easy!!

No, don't set to cracking for using it under BC. It should be the consistency of peanut butter. It takes 2-4 hours in your fridge or overnight left out on the counter. You can smooth it with a hot knife to get sharp edges once you get it on the cake and relatively even and smooth.
Your ratio needs to change when you use wh choc or milk choc (3:1). I also use whipping cream. Rylan explains it well. Check this out - it will help :
http://www.artandappetite.com/2009/11/ganache-instead-of-buttercream/
Have fun and good luck!