Office Web App will not run correctly

I have installed Sharepoint 2013 and Office Web Apps in a test environment as detailed by Microsoft documentation.

Sharepoint is set up and working correctly and the Office Web App server seems to be running fine.

As I am in a test environment I have no need to use HTTPS so I have changed the SPWOPI zone to internal-http, I have also changed .AllowOAuthOverHttp to true.

All bindings are in place and seeing as I have added a domain using New-OfficeWebAppsHost I have been logging on using a domain client, despite all of this each time you attempt to open a document I receive an error message (oddly enough each web app had a different error message).

I amcompletely puzzled now, and any help would be much appreciated.

Thanks

Daryl