WordPress creating wrong url for images in subdomain

I am setting up a WordPress site and am having problems with images in a subdomain. The WordPress installation is in a subdirectory.
https://www.mydomain.uk/directory-name

and the subdomain is

https://images.mydomain.uk/originals

Originals is a folder on the subdomain.

I have changed wp-config.php to

define(‘UPLOADS’, ‘../images/originals’);
inserted just above the line that says require_once(ABSPATH.’wp-settings.php’);.

and in options.php

Store uploads in this folder
../images/originals

 Full URL path to files
 https://images.mydomain.uk/originals

The images are going into the right place and an image displays if I manually type the url in to the browser address bar.
https://images.mydomain.uk/originals/filename-300×158.jpg

However when I insert an image in to a page the image url becomes
https://www.mydomain.uk/directory-name/../images/originals/filename-300×158.jpg
This is how it is inserted in the database guid field. Although it does work it is not what is wanted and defeats the point of the subdomain.
Any suggestions?