Ok, don't bother to ask how I know about this, but:
If you have recently purchased them, they may be multi-voltage, that is they will work on 110/240v - check the cord, the box or do some google searching on your particular model.
If they are GHDs and the Mk4 version (USD100 sounds about right), then they are mulit-voltage and you don't need to buy the power converter, you can just use a simple plug adaptor - Case solved.