Where can i sell my iphone 4?

If you use a mobile phone recycling comparison site you can see how much cash you can get from all of the main UK phone recyclers. According to http://www.sellmyoldmobilephone.co.uk/brand/Apple/m-iPhone-4G-16GB today, the best price for the 16Gb iPhone 4 is �330, but the price history at the bottom of the page shows the value is dropping, so I'd sell it now if I were you. There are customer reviews of the recyclers too, which should help you to trust them a bit.