Cheap iphone from buying in usa?

I was looking on the us apple website and saw the iphone c was $100.
so i thought could i buy that iphone get it send to an american address, get it unlocked then send over here consequently i save around 200 pounds?
will i be able to use a sim from uk? Will this work?

The $100 is a deposit on a 2 year contract; it is not the full price of the phone. You would have to set up a contract with a US network, and pay the monthly tariff on it for the life of the contract. It is the same principle as here in the UK, where you may pay an upfront fee, then pay the monthly contract as well. Obviously, to set up a contract on a US network, you would have to have a credit rating over there, as you would in the UK. As for using a UK sim, this may not work anyway, as the frequencies are different in the US compared to the UK. However, even if the sim does work, you still have to deal with the contract issue, as I explained above.