Needless to say I accept no responsibility for any of this information, it all worked great for me, I was prepared to try it because I needed the thing app unocked and if I had to put it in for service I felt it might as well be bricked
To get the firmware files, download and run the latest executable ruu_spl_wwe.exe, from clubimate and enter the IMEI when requested. Leave the disclaimer screen up unanswered without clicking "next".
The files you need are WMIPL.DIP ~ 1 meg and WMUPDAT.DIP ~ 48 meg which are extracted by the installer to a random directory on your temp path. Locate and copy these files somewhere safe, then cancel the ROM update utility as it's job is done.
Place the two files into the root of an SD card of appropriate capacity. As a precaution at this stage I backed up everything else on the card though in the event it was not erased when I did the flash.
Power the phone off, remove the SIM for safety and insert the SD card, replace the battery etc.
Press and hold 6 and then press the red handset button to power on. Keep 6 held down. The phone will power up and display a rectangular status box across the screen, you can release the buttons now. This box will gradually fill left to right and once filled, the phone will reboot, and hopefully with the latest firmware loaded!