Last month, O2 Germany announced the availability of Windows Mobile 6 upgrades for the Xda Orbit and Xda trion. Now, O2 UK has also announced the upgrades (here for the Xda Orbit and here for the Xda trion).
Your device serial number will be required for the download. The serial number can be found on your Xda when you remove the battery pack. Once you’ve removed it the serial number will be clearly visible in white text on the device. (Example: S/N HTxxxxxxxxxxxxxx or S/N: SZxxxxxxxxxxxxxx)
Note: The upgrade will replace the current ROM image and will erase partnership and all user data and programs on your device. Be sure to back everything up before you start.
Source: the::unwired