Hi
admittedly its tucked away and we should make it more prominent but if you visit our Guidance and Support page
xerte.org.uk/index.php/en/support-menu/support
then at the bottom of that page there's an accordion pane named Commercial support. That pane contains the following info:
If you need commercial support with establishing, troubleshooting or upgrading your installation, hosting Xerte, custom developments, training, or any other Xerte support then we highly recommend the following companies who are directly involved in and directly contribute to the Xerte project. You can contact them via the following links:
mitchellmedia.co.uk
|
xerteacademy.com
|
learningapps.co.uk
|
delearning.nl
Each are longstanding members of the Xerte community and provide excellent service at great prices.
Some of those links also in my sig and as you're UK based you would be referred to me anyway!

HTH
Ron