I do agree with you Roadster that the vote is for the people of Scotland, regardless of who else in the UK it affects.
The UK is set to have a vote on whether to stay in the EU or not, and you can imagine the reaction if it became known that the vote was to be extended to the entire EU (it would, after all, affect them also). Just imagine the situation if the UK voted to leave, but Germany, France, etc, said no, and we had to stay (doesn't sound too democratic).