Funkydoodycool is 100% correct....
You can only get keys cut to fit your car from MB in Germany.
And....when the keys arrive at you local MB/Smart dealer, they
are currently the only one's who can then TAN code it to your car.
Without the TAN code the key will not imobilise the alarm or start the car.
The car came with 2 keys when new....and the cost to replace any keys that
have been lost or damaged is a penalty for loosing them.
In the UK a new key costs £200 +£50 to code it.
It sounds a lot....but if it was an MB key or one for a Punto or Renault the cost
for a new electronic key would be around the £800+ mark ! !