And the advice for where you can legally place a dashcam only mentions places at the edge of the screen or behind the rear-view mirror - places which the windscreen wipers don't clear, so useless in rain. I put mine behind the area obscured by the passenger sun visor, right at the top of the area cleared by the passenger wiper.
At least we haven't prohibited the use of dashcams on privacy grounds, unlike some European countries. My feeling is that anything which happens on the road is a "public place" and you shouldn't have any expectation of privacy.