Step 1:

You need to whitelist our domain.

Within Google Maps API Console - you need to find your key and click edit.

Under Website Restrictions, click Add an item:

You should then enter the following and click Done.

*.supercontrol.co.uk/*

For more information, you can follow this guide.

https://developers.google.com/maps/documentation/javascript/get-api-key#restrict_key 

Step 2:

Once the above has been completed, ensure that within your SuperControl account you have entered your Google API key. This can be added via Admin menu > Integration HTML. 

This will then resolve the Referer Not Allowed error.