Alright buddy, used to work for Halfords, if you don't have the receipt ask the store you bought the headunit from nicely and they may be able to look up on their system and print it off again for you. Although, Halford's are currently undergoing an IT system/till change so if you bought the cd player before the store was converted...if it has been, then they probably won't be able to go back over the records and print it off for you. But worth a try anyway!
After first month then cd player has to get sent off for repair.
Hope that helps!