I'm using the DSC Extension in Azure to configure the VM's and on first deployment that works fine. However, if I've made an error in the DSC script or need to amend it I am having trouble understanding how to force the VM to download the new configuration.
My DSC files are stored in Azure blob storage as required by the extensions, so I am uploading a new version of the zip here. Should this automatically trigger the VM to download the new file, or do I need to run a command to do so?
No, it won't automatically trigger.
Once you've uploaded your configuration to the correct azure blob you still need to push the configuration to your VM.
You can do this by using the Set-AzureVMDscExtension cmdlet.