This is a nice idea. My UX suggestions:

- display the heatmap first - have a prominent link saying something like: add your vote to the map. When someone clicks that link, ask them to enter their location (city or town and country), then ask them the same question the Scots will vote for in the referendum: Should Scotland be an independent country? Yes/No.

I think the auto-detect location causes too many problems and may have privacy implications if, as another poster says, you can identify quite precise locations.

What would be really nice would be a map similar to the Book Depository ("Watch people shop" map):

http://www.bookdepository.com/live

In this case, you would display a pop-up each time someone voted with the name of their town or city and whether they'd voted Yes or No.