SWAP!! Iphone 4 for good android phone -

Hi i have a iphone 4 16gb black i do not have the box i use this phone on vodafone but i baught it from carphone werehouse and as far as i know it is open to all networks but have not checked yet it I got this phone about a year ago but it is in really good condition has had a screen cover on it and a cover on the back so just about no scratchs at all i would like to swap this iphone for a good android phone as i want to try out android phones as i have had a iphone since the first one all offers will be consided but has to be a good one i would really like a htc one x that would be ideal