Setup Process
I was unable to get this AMI working in the first instance, I therefore contacted CloudLinux support who replied in just a few minutes which was excellent and after a few e-mails I was able to access WHM. I have put together a short guide of the steps I had to do to get it working just incase it helps anyone else:
1. SSH to the instance hostname/IP address using username ec2-user and the certificate file you specified for the instance
2. Run command 'sudo su' (without quotes) to get root access.
3. Run command 'whmapi1 create_user_session user=root service=whostmgrd locale=en' (without quotes) to generate a first-time login link. You may notice that the IP address at the beginning of the URL doesn't match your EC2 instance, in which case you should replace it with the correct IP address.
4. Open the link in your web browser. Note: the most recent versions of Chrome block access to HTTPS sites that don't have a valid certificate so you may need to use a different browser to bypass this. You can set up HTTPS once logged in.
That works :)