I found 3 companies that offer unlocking for the Lumia 920 (2 of them have similar urls so could be owned by the same people). The only UK based one wanted ?51 to unlock and said it could take 4-18 business days. The other two want $39.99 (?25) to unlock so I've gone with
Cellunlocker.net - #1 Unlock Codes for Network Cell Phone Unlocking who say they will have it done in 3-10 business days. I heard a rumour they told someone they cant unlock phones for 3-4 weeks so I contacted them myself and just got a reply saying they will definitely be giving me the unlock code within 3-10 business days so at this point it's a waiting game. They deal through paypal so I figure if anything goes wrong I can get a refund. On their site they say if you can prove (by video) their code doesn't unlock the phone they will refund you in full.
So this is the latest I've found out. I called every unlocking service within my local area and none of them can unlock this phone and don't know when they will be able to.