Charlie,
All Apple chargers in recent years are designed for multi-voltage operation from 100-240 VAC, so all you'll need is Plug Adaptors specific to the areas you'll be travelling. All of my Apple products use two-pin plugs so a non-grounding Plug Adaptor will be fine. As someone else mentioned, if you'll be travelling in the U.K. as well as the continent, you'll need two different models of Plug Adaptors.
I'm not sure what you mean by "protect the computer"? You won't need a Voltage Converter as the Apple chargers are designed to provide the proper voltage to the computer / phone / iPad. The function of the Plug Adaptor is to allow the North American style plugs to be connected to European outlets, which have a different pin configuration.