iphone 3gs 16gb full working condition on o2 !

i have my iphone 3gs up for sale, its in full working order and locked to o2. It is 16gb memory and has always had a screen protector on so the screen will be immaculate. General wear to the back as not had a case on. All up to date and running on the latest software. I do have the box somewhere so if i have time to look for it i will include it. I have the mains plug and usb lead. Asking for £120 ovno. Can deliver for cost of petrol.