Going off topic a bit, but related to the prosecutions bit, I heard an interesting tale on a LBC phone in the other day from a chap who was prosecuted for not providing a specimen of breath... as a passenger in a car.
He accepted a lift from a friend, and said friend was subsequently pulled over. Instead of keeping his mouth shut, he (the passenger) admitted that he got a bit lippy protesting his friend's innocence, and the Police then asked him for a sample of breath.
Being the passenger, he refused, and was successfully prosecuted for refusal. He said that the magistrate said that it was a highly unusual case, but apparently the Police can stop you anywhere and demand a breath test - including if you are walking down the street - refusal to provide a specimen is the specific offence, and the sentence is the same, driving ban and/or points etc..
He said that he learned to keep shtum in future.