On mine they don't come on when you turn on the rear defroster. I don't know how the Euro version is, but on mine, there's a little knob to adjust your mirrors right in fron of the handle to open the door from the inside. It has 3 different settings, one for the left mirror which is on top, one for the right mirror which is all the way down and one in the middle that looks like a little window with heat comin off of it. You put it in that middle spot to heat up the mirrors, but leave it on either the right or left mirror when you don't need it.
Like I said, don't know how the Euro version is, but I hope this helps some.