I have just spoken to site grounds support about why I can't change the wordpress and site address in the general settings and this is their response. It seems that you are handing out conflicting advice. Maybe the better thing for me to do is just push the site live as it is and deal with the issues on the live site?
---Siteground support message;
The provided article states correctly about the URLs of our staging tool.
Let me try to explain how our staging software works.
When creating a WordPress staging copy we do not replace the Home and SiteUrl options for WordPress. They remain the same as the original website. Instead, we use three additional Apache modules that allow you to actually work on the correct application:
mod_host – all the requests to the application will be processed as they have been made to the real hostname (in our case all of the requests to the stagingN.domain.com and not the URL in the WordPress configuration). This module is written by us.
mod_substitute – standard Apache module – used for replacing strings in the Apache’s response. We use this to replace domain.com with stagingN.domain.com
mod_headers – standard Apache module – used for changing request and response headers. Used for configuring the headers according to the staging subdomain.
This is why the database URL of the staging copy has to be the live site ones instead of the staging ones otherwise the redirect loop error occurs.
We have thoroughly tested the staging software with multiple different WordPress applications and our tests show it is working as expected. Still, unfortunately, we cannot give a guarantee it will not have discrepancies with other third-party plugins/themes and/or custom code added to WordPress.
If you are having troubles using any theme or plugin on the staging site we would advise you to clone your website by using a real subdomain for that purpose. For example, you can create a new subdomain titled new.jonathan-sainsbury.com from your cPanel -> Subdomains tab. Then clone your live site into new.jonathan-sainsbury.com and reconfigure the site to work with the new URL. You can clone the site by using your cPanel -> Softaculous tool -> Scripts Installations and click on the "Clone" icon next to Clone Installation Details.
This way the staging site will use a real subdomain (new.jonathan-sainsbury.com) and the "WooCommerce Composite Products" plugin will work properly. The disadvantages of this method are that you will not be able to push the staging site to live directly but you should copy the staging site over the live one and manually reconfigure it to use the live site's domain name (jonathan-sainsbury.com) instead of the staging one (new.jonathan-sainsbury.com).
Should you have any further questions regarding our services do not hesitate to contact us at any time
Technical Support Team