Help Unlocking a Desire from Orange

[Lubalin]

I've rooted my Orange Desire and flashed a custom ROM. Now my contract is up and I'd like to move to GiffGaff.

I'm assuming the phone is locked to Orange. How do I go about unlocking it so I can use the Giffgaff SIM?

Thanks in advance.

 

[Hadron]

I posted an answer in this thread recently: http://androidforums.com/showthread.php?t=586164