Can I buy an unlocked iPhone 4s from the US and use my o2 contract sim in it?

Is it possible for me to buy an unlocked iPhone 4s from the US, then use my o2 sim card (contract) in it? If so would I be lose any services available to those who purchased their iPhone in the UK?

You can buy a iPhone from us and then unlock it

Based on how I understand an unlocked iPhone, you can insert any SIM card you want as long as it is compatible. If you get an unlocked iPhone 4s and you want an O2 SIM, I believe it will function.

Yes it is possible. Though I would buy it from a UK Apple Store.

If you buy unlocked iPhone you could use any sim you want, but unlocked iPhone price to high (almost 100$) higher. I recommend you to purchase AT&T USA lock mobile and use unlocked services to unlock you iPhone under $11 USD from http://iphoneitune.com/att-usa-factory-unlock.html

Yeah unlocked phone has all privileges that any carriers can be supported. But the only drawback in buying an unlocked phone is the cost. You will end up in paying a couple of hundreds of dollars. Instead you can buy a locked phone and unlock it via third party vendors like http://www.theunlockspot.com/apple-iphone-4s/rs16wp9/ by just spending few in it. They will unlock your Iphone using remote unlocking method, which serves best and safest mean to unlock Iphones. You won't lose any service once unlocked.

Yes you can definitely do that with an unlocked iPhone