2G 3.1.2 unlocking help

[shanfoley]

Hi, I recently, stupidly, updated my uk bought, jailbroken, 2G iphone to 3.1.2 via itunes, so now the baseband has also been updated so i can't use it in NZ, where i live. Is there any way to fix this yet, or can i downgrade, and what about re-jailbreaking or re adding cydia and Icy? Not really sure about anything so any help in lamens terms would be much appreciated,
Thanks