Is the Five Pound coin worth more than its value?
A coin collector would pay more than £5 for the coin, if it was uncirculated and in Mint condition, or a Proof coin. However if you were to go into a bank and exchange the coin for other currency, they would only give you the face value of £5's worth.
At worst, it is legal tender in Britain and it is worth Five pounds. The British decimal Five Pound coin is intended to be a Commemorative coin or for serious collectors or investors. Any value above Five Pounds would depend on the condition of the coin, what it is made from, the year and possibly the design.