At least on my older mag safe charger, only 2 pins are connected. You can pull off the UK plug and plug in the US or EU one, or even just a regular figure 8 lead (not sure of the correct name for these!)
Had a few times where I've had to disconnect the charger as I could feel an effect like static electricity on the metal case of the MacBook.
Had a few times where I've had to disconnect the charger as I could feel an effect like static electricity on the metal case of the MacBook.