Editing a module seems to have no effect - magento

Question

I am using a module which calculates the shipping method based on item weight. The module appears to install but if I make an edit to the main class, nothing seems to be reflected on the front end.
The main class extends the Mage_Shipping_Model_Carrier_Abstract see below:
<?php
class Laurensmedia_Advancedshipping_Model_Carrier_Advancedshipping
extends Mage_Shipping_Model_Carrier_Abstract
implements Mage_Shipping_Model_Carrier_Interface
{
protected $_code = 'advancedshipping';
The config.xml file looks like this:
<?xml version="1.0"?>
<config>
<modules>
<Laurensmedia_Advancedshipping>
<version>0.1.0</version>
</Laurensmedia_Advancedshipping>
</modules>
<global>
<helpers>
<advancedshipping>
<class>Laurensmedia_Advancedshipping_Helper</class>
</advancedshipping>
</helpers>
<blocks>
<advancedshipping>
<class>Laurensmedia_Advancedshipping_Block</class>
</advancedshipping>
</blocks>
<models>
<advancedshipping>
<class>Laurensmedia_Advancedshipping_Model</class>
<resourceModel>advancedshipping_mysql4</resourceModel>
</advancedshipping>
<advancedshipping_mysql4>
<class>Laurensmedia_Advancedshipping_Model_Mysql4</class>
<entities>
<matrix>
<table>advancedshipping_matrix</table>
</matrix>
</entities>
</advancedshipping_mysql4>
<shipping>
<rewrite>
<shipping>Laurensmedia_Advancedshipping_Model_Shipping_Shipping</shipping>
</rewrite>
</shipping>
</models>
<resources>
<advancedshipping_setup>
<setup>
<module>Laurensmedia_Advancedshipping</module>
</setup>
<connection>
<use>core_setup</use>
</connection>
</advancedshipping_setup>
<advancedshipping_write>
<connection>
<use>core_write</use>
</connection>
</advancedshipping_write>
<advancedshipping_read>
<connection>
<use>core_read</use>
</connection>
</advancedshipping_read>
</resources>
</global>
<admin>
<routers>
<advancedshipping>
<use>admin</use>
<args>
<module>Laurensmedia_Advancedshipping</module>
<frontName>advancedshipping</frontName>
</args>
</advancedshipping>
</routers>
</admin>
<adminhtml>
<menu>
<advancedshipping module="advancedshipping">
<title>Advancedshipping</title>
<sort_order>100</sort_order>
<children>
<matrix module="advancedshipping">
<title>Manage Matrix</title>
<sort_order>0</sort_order>
<action>advancedshipping/adminhtml_matrix</action>
</matrix>
<import module="advancedshipping">
<title>Import from CSV</title>
<sort_order>1</sort_order>
<action>advancedshipping/adminhtml_matrix/import</action>
</import>
<settings>
<title>Manage Settings</title>
<sort_order>999</sort_order>
<action>adminhtml/system_config/edit/section/lm_advancedshipping</action>
</settings>
</children>
</advancedshipping>
</menu>
<acl>
<resources>
<all>
<title>Allow Everything</title>
</all>
<admin>
<children>
<advancedshipping translate="title" module="advancedshipping">
<title>Advancedshipping</title>
<sort_order>1000</sort_order>
<children>
<matrix translate="title">
<title>Manage Matrix</title>
<sort_order>0</sort_order>
</matrix>
<import translate="title">
<title>Import from CSV</title>
<sort_order>1</sort_order>
</import>
<settings translate="title">
<title>Manage Settings</title>
<sort_order>999</sort_order>
</settings>
</children>
</advancedshipping>
</children>
</admin>
</resources>
</acl>
<layout>
<updates>
<advancedshipping>
<file>advancedshipping.xml</file>
</advancedshipping>
</updates>
</layout>
</adminhtml>
<default>
<carriers>
<advancedshipping>
<active>1</active>
<model>advancedshipping/carrier_advancedshipping</model>
<name>Advanced Shipping</name>
<title>Laurensmedia</title>
<description>Laurensmedia Advanced Shipping description</description>
<sort_order>0</sort_order>
</advancedshipping>
</carriers>
</default>
</config>
I have tried the following:
Clearing the Magneto cache
Manually deleting the contents of /var/cache/
Copying all of the other modules to ../disabled/ (Effectively
disabling them)
None of the above seems to have worked. Can anyone offer any suggestions as to why when I edit the main class file nothing happens? Even if I deliberately break the file (i.e - delete half the code) I don't even see any errors.

Answer 1

I don't see a <rewrite> declared for Laurensmedia_Advancedshipping_Model_Carrier_Advancedshipping in the config.
That would explain why it's not being picked up, since it appears to want to rewrite a standard Magento class.
If it's not intended as a rewrite, how is that class being called?