1. Install any file manager (for ex: Total Commander)
2. Open /efs/imei/mps_code.dat file and modify it with CSC which you need BTU for UK (CSC must be included in the firmware)
3. Turn off the tablet, hold VolumeUP + Power (This is needed to enter tablet into the recovery mode), in recovery you will see text like "Applied Multi-CSC:BTU "
4. That's it.
You may find that you need root on anything above ICS.