Quick note;
When I did this but, "$lang['Cpanel.service_field.domain'] = "Please enter the full domain name you wish to host";" appeared at the top of every page, except when I went through the wizard and got to step 2 and then that was the only thing which appeared on the page! Just completely white, with that at the top. I'm not bothered, I'm very happy as the first part of your post has solved my question anyway! I just took it out again and will remember to check after any upgrades.
Stuart
Nevermind, figured out what I did. I pasted it in after the "?>" closing the php off. Oops......