Removing forum header from Sign Up / Register screens

[lynx31]

I'm trying to remove our header banner so that it will only become visable once the user is signed up and registered for what is a private VBulletin forum.

I've managed to remove it from the standard index.php log in page by going to the STANDARD_ERROR template and replacing $header with <if condition="$bbuserinfo[userid]">$header</if>

The problem is, once you click 'sign up' from the index.php page the logo then reappears on the signup page (where the terms and conditions need to be ticked and accepted, and on further pages such as where they fill in their registration details.

I'm pretty new to this - does anyone know the exact templates I need to edit to remove the logo/header from view completely until the user is fully signed up and has access to the private board?

(have I overlooked an easier method other than changing all the templates to make this logo invisible to non-members? a simple on / off button on the Admin CP seems a good idea in future)

any help appreciated - thanks!