I'm trying to create a plugin to allow shipping cost based on ranges of post codes. The post codes are hard-coded into the plugin. Due to my lack of experience developing for ExpressionEngine I'm unable to get the plugin to do anything.
Note that the cart only has one shipping option; the user shouldn't need to or be able to select a shipping option; this should be applied automatically based on their shipping post code.
Plugin: https://gist.github.com/anonymous/86838c02028faabfb404