How to update $settings for a custom shipping plugin

In the process of writing an Australia Post plugin I have made changes to the following array in the on_creation function. This is similar to the services array in the UPS shipping plugin for example.

$this->domestic_services = array(

		'AUS_PARCEL_REGULAR'    				=> new Aus_Post_Service('AUS_PARCEL_REGULAR', 				__('Regular Parcel Post', 'mp'),			'22'),
		'AUS_PARCEL_EXPRESS'  					=> new Aus_Post_Service('AUS_PARCEL_EXPRESS', 				__('Express Parcel Post', 'mp'),  			'22'),


I have made changes in this as I have altered how I am setting things up. However when I call $this->auspost_settings['domestic_services'] I am getting the old information that used to be in that array.

Is this data being stored somewhere in Marketpress - maybe settings['shipping']['myplugin'] ? If so, how do I reset it?