Starting with version 2018.1, you can specify the format for value references related to date/time properties. For details, have a look at section Format of date/time value references of the following help article: https://www.adaxes.com/help/ValueReferences/#format-of-date/time-value-references.
Currently, the format in which date/time value references are inserted in emails depends on the system locale on the computer where Adaxes service is installed. Thus, you can change the system locale to UK to change the date format in the value references.
Alternatively, you can send e-mails with the help of PowerShell scripts. For information on sending emails with scripts, see Sending Emails and SMS. In the script, you can get the date using the Get-Date built-in PowerShell cmdlet that provides you a variety of ways how to convert a date to a string. For more information, see Get-Date.