You can create a filter or filter group to spot them all and then act on them manually. (Iwould really like to say use JS but this is not supporting time zones yet, only language settings or profiles but those also don'T provide possibility to target by time zone)

Btw. to ensure the devices don't run into your system (a second time) you could create a new Samsung knox policy providing them a wrong enrollment ID like "Stolen Device". Then they won't ever end up in your environment again.
Ofc you need to reroute each single stolen device once to this rule but doing so will finally mean less work and the device is somehow stuck on the agent enrollment screen and no Soti license is consumed.

Based on your brief description,  I assume all your devices are using Samsung Knox Mobile Enrollment (KME) for automated re-enrollment of factory reset devices to MobiControl.

Assume you have N group of devices for operations in N different countries, and one of them is UK.  Then, I think you should create N device enrollment policies, and each can have a  corresponding country device sub-group as the target location for device enrolled with the policy..  Then for each of the N group of devices, configure in Samsung Knox Portal to have such devices (based on their hardware serial number) associated with the enrollment ID/URL of the corresponding group.  In this way, any device assigned in operation in the nth country will always be enrolled back to the same nth device sub-group after any factory-reset event.   All of these enrollment target device sub-group should have kiosk/lockdown policy (required for assumed lost/stolen devices) assigned.   If a device that is not lost/stolen gets factory reset, administrator can  manually relocate such device to a production device-group for that country..

This should be much more reliable & systematic than your mentioned approaches based on location/geofence or time-zone.