I will always refuse as long as I have the option.... The police seem to have an attitude when they are questioned with anything. I recently had an attitude given to me at a hastily constructed breatheliser stop point.

I pointed out a couple of flashing lights in the road does not a check-point make, it could have been an accident which I was slowly circumnavigating before the officer jumped out from his vehicle and waved me angrily over.
I had to shake my head after blowing into the machine, before pulling away, content with the fact he believed he could detain me on something.
Sad we have come to the point of peacekeepers having delusions of grandeur.