Issue with migrating a website and setting up a dedicated VPS server with VPS.NET

Hello WPMU Dev Support,

Will describe this issue but more hoping for a suggestion to try out than the definitive answer.

A client has purchased a dedicated cloud server from VPS.NET and has requested I move all his websites over from CoolHandle where there have been many performance issues.

It is my first time using cPanel WHM, have only ever used cPanel, have worked my way through setting up a VPS, domain name, configuring PHP, Apache, binding domains to an IP Address etc. Have even installed Varnish Cache and have the freedom to switch on Fast CGI.

After going through all of this steep learning curve I am left with the following odd and frustating issue:

1) I transfered across the website (on CoolHandle) to (VPS.NET) using backupbuddy, to my mamzement all went smoothly.

2) When I am logged in as the admin user loks and behaves as it should do, with a performance increase that is 20 times faster than on CoolHandle

3) When I am not logged in and look at then the header image does not show and on the contact page there are PHP function errors

Am guessing that there has got to be a setting via the cPanel WHM for PHP but I simply vannot work out what this is, have gone through everything that comes up in Google and still cannot track a solution down for this issue.

VPS.NET charge $10 for support to resolve this, I have actually paid and awaiting for them to get back but they seem genuinely confused about this too. Does anyone have an idea or provide a link to a page which might have the solution to this truly frustrating problem?

Would be most grateful for any suggestions.

Kind regards,