Im seriously considering selling my N97 and picking up an Iphone.

Just wondering which ones with 3.1.2 firmware will work with 3 mobile. I know it wouldn't work if the phone was on 3.1.3.

If I get a 2G then I might keep both and just use the 2G for apps so not too much of an issue for that. However, if I get a 3G/3GS then it would be my only phone so it would need to work on 3 mobile as my contract is with them for another year.

If you get one that was originally an O2 iPhone then you can get it unlocked officially anyway, even if you aren't the original purchaser - you'll just need an O2 PAYG SIM with at least £15 on and fill in the form on this page of their website. Unlocking costs £15 this way (it's free if you have an O2 contract SIM you can use) but it won't matter what firmware you have and will also mean it will stay unlocked permanently no matter what firmware upgrades you apply in the future - no need to muck around with jailbreaking. This will of course also work with a brand new PAYG O2 iPhone (and I believe Tesco PAYG iPhones can also be unlocked by O2 too if you want to benefit from clubcard points etc.).

You'll just need to put the O2 SIM (PAYG or contract) in the phone with it turned on so that it can get an O2 signal and register on their network - then O2 will be able to match the SIM to the IMEI when you request the unlock.

If depends on if it is factory unlocked or not. Basically if it is factory unlocked like mine is on 3. It will work on any network in the world and on any firmware. Whether it is jailbroken or not. You can't get factory unlocked iphones in this country officially you can get them from ebay, but you pay a bit more for them.They are usually imported from Hong Kong or Belgium or France. Where you can buy them unlocked.

If you buy one from O2 or Orange in the UK it will be locked to that network. Then there are two ways to get it to work on a different network one option is to Jailbreak it or to request a unlock from those networks. Some 3gs iphones running on 3.1.3 can be unlocked but it must be the one fitted with an older boot rom. They changed the boot rom in the phone after week 40 last year. If your phone is newer than that it cannot be jailbroken on that firmware. You can check how old it is by checking the serial number on the phone. It is the 4th and 5th digit you need to look for and it will need to be less than 40. But if it is on the 3.1.2 firmware with the newer boot rom it can be Jailbroken very easily by using blackrain. But there is a catch every time you switch it off you will need to link the phone up to your computer via the black rain programme to get it to boot up. But if you have an older boot rom in the iphone, then you will not need to use your computer everytime you switch your phone on.

Hope that helps

Thanks for the replies guys. Just so I understood that correctly:
Factory Unocked = Instant Joy!
Firmware 3.1.2/3.1.3 + New Bootrom = Possible but needs doing each time its turned off.
Firmware 3.1.2/3.1.3 + Old Bootrom = No problems.

EDIT: Just speaking to a colleague who has an Iphone 3G and he said the the baseband can also play a part in unlocking/jailbreaking. Anything to look out for there?

Ideally I would an Unlocked and Jailbroken Iphone that works on 3 mobile.

Yes what you say just about sums it up.

About the baseband if it is on firmware 3.1.2 it will be on the older baseband. So you will be ok to jailbreak it. If you upgrade the firmware it will also upgrade your baseband too. Which will make it not possible to jailbreak with the new boot rom.

In the past i was always a Nokia fan and i always bought the latest phone from them. I changed to an iphone because i felt that the Symbian os system has never really been updated to work well with a smart phone and its often unreliable. Also the selection of apps are poor compared to apples apps store.

Hope that helps

Those are the exact reasons why Im changing. I would consider Android but was hoping for the Desire. Dont want to wait for that.

I'd just like to clarify that getting an O2 iPhone officially unlocked by O2 will make it indistinguishable from a factory unlocked iPhone - that is definitely the route I would recommend for anyone wanting to use an iPhone on another network, especially as you can get even a brand new one unlocked immediately by O2 for £15 (or for free if you happen to have an O2 contract SIM you can use/borrow for a couple of minutes).

As you can see, going the unofficial / jailbreak route gets very confusing very quickly with having to worry about firmware versions, basebands and bootroms - and it's like this each time Apple releases a new firmware! For example if an iPhone 3GS has already been updated to 3.1.3 officially then it will have had its baseband updated and therefore can't be unlocked, regardless of what bootrom version it has.

O2 have made it so easy to do it all officially that IMHO it's crazy not to!