Help In UK - can I use the US Gingerbread update?

[Lau May]

I am in the UK and I have just purchased a second hand Atrix via ebay. Although the seller is in the UK the mobile is described as an AT&T Unlocked phone. I am therefore guessing that it is an imported (US) model - as models sold here in the UK are usually Orange or T-Mobile.

If it's an AT&T model (although now unlocked) can I use the US Motorola gingerbread update?

There has been a lot of complaints here in the UK about the delay with the UK gingerbread update. But if my phone is an AT&T model, which update applies to me? I have read that the hardware differs.

Also, if I decide to go down the custom rom route - does it make a difference which model I have?

Thanks.