Hi Paul,
Greetings from Syncfusion support.
We checked this scenario by creating a sample and applying en-GB as default culture to the application. We could display proper format for the column in the sample from our side. Please download the sample from the link below,
Kindly refer the above attachments and modify your application. And if you are still facing difficulties then kindly share with us a simple issue reproducing sample for us to validate based on your scenario.
Regards,
Renjith R