Still nothing of any substance from the police or CPS over the threat to kill me. However somebody posting under the name 'innocent and proven so by police' is almost certainly the motorist involved and he has posted his account of the incident here. Road CC have kindly added my unedited footage to the page so we can all enjoy a 'spot the difference' competition between his account and my video. Whether it is true that the police have interviewed him and declared him innocent I have yet to discover, but I have contacted the police for an update.
Meanwhile I have heard back from my MP who has agreed to raise my concerns about the over-use of police cautions with the Home Secretary. I am hoping for a more substantive reply in due course.