Autel IM508 and XP200 (no need XP400) is able to add a new key and program all keys lost for 2006 Bentley GT.
Dismantle and read the KESSY module, there is video in the IM508 table, you can follow it to do.
Look at this image showing where is the video located in the tablet.
These videos show how to dismantle the module off the car, and to use XP200 programmer to read the corresponding the immobilizer data including eeprom, mcu and ECU, as well as remote renew.
Good to know:
XP200 Programmer is enough, no need XP400, XP200 is able to read 8pin chip.