I am sure I have read a similar thread on here about scan where a forum user's order was short of a cpu. I have searched but cannot find it.
I am not an expert, I would advise you to contact your local citizin's advice bureau for how to proceed.
When you acceted delivery, how did you sign for the delivery, did you sign not inspected or not checked? You should always do this unless you open the order in front of the delivery driver.