Phones4U have the refurbished Samsung P300 Credit-Card-sized phone on their website for £149.95 on Orange pay as you go. If you purchase via QuidCo.com you'll get £5 cashback, meaning you're paying just £144.95 for the phone.
The Samsung P300 is a tiny, credit card sized phone. It's just 8.9mm thin and weighs 65g. The P300 still packs in a 1.3 megapixel camera with video record, MP3 player, Bluetooth and a speakerphone.