Thanks guys. My 3GS is now unlocked and my Orange simcard is now working without the aid of temporary jailbreaks. Ordered Sunday, received unlock confirmation on Thursday.
If you do have a phone that has jailbreak software on it, the process may be slightly different. In my case I was on firmware from 2010 (v4.0.1). Itunes told me I had to restore to factory settings and then my firmware was updated. Bit annoying as I've had to spend a couple of hours in the App Store and I've lost paid apps. There may be a solution to this that I've missed. I suggest if you have any questions - email officialiphoneunlock before you buy.
Wish I knew about this service earlier
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