Do be warned though that many retailers are very aware of people bringing back broken components on someone elses receipt and they often put little stickers or marks on the components to identify them as coming from a particular shop. At least 3 of OcUK biggest competitors do this - one even sticks a sticker across middle of the bottom of the CPU with their name and tracking number on! if you do take the CPU back on someone elses receipt it could be construed as fraud, so just be aware...
Is that just in the case of OEM cpu's?