One wouldn't use a fuse rated at 125 V in a 250 V circuit even if the current rating was appropriate. Why? Because when the fuse blows, it must be designed to contain the arc and melted metal. If a fuse is used at a voltage higher than it's designed for, it may not contain the melted metal and the arc when it blows. There's not a problem in using a fuse in a circuit at a lower voltage than it's rated for.

Thanks for the correction.

Cheers,
Scott.