So I installed and finished setting up the WHMCS integration plugin.
I also use the tutorial videos template within WHMCS, that comes with it and now I get the red box of:
Sorry this doesn't look like a WHMCS site at [http://www.wesh.co.uk/customer.services/] Make sure your WHMCS Integration settings are pointing to the correct URL and that the WHMCS site is set for the Portal template in Setup | General.
My WHMCS is set to "Portal" and I have used the correct URL, but if I go to http://www.wesh.co.uk/customer.services/ which works, and then click on tutorials, then click on one of the tutorials, this is where I now get the red box.
Going directly to the tutorials page @ http://www.wesh.co.uk/customer.services/tutorials.php works perfectly, but only when trying to view them via the WHMCS integration URL they dont work.