If i buy an iphone 5s of apple store usa will it work in uk?

Okay so i have done alot of research on this and so far i'm 80% sure if i buy an unlocked iphone 5s on the apple store usa for $649 which is about £410 that i will be able to insert an o2 sim card and activate it instead of activating the t mobile sim which comes with it. So my concerns are that i won't be able to and/or i will be charged international charges so could you please help me out here as it will save me around £150 doing this if possible.

It should

I don't think you can, If you are on the 'US' apple store it will only let you ship to the US when you try to order it. Tried it already with Ireland cause it will cost me an extra €210 to buy it here. Its not fair.

It would providing you get it unlocked or it comes unlocked, i done this with the iphone 5, it came locked so i unlocked it on unlock-4.me then it was working as if it had just come out my local apple store!