I don't see a solution to this, so I'll tend to believe the cynic's viewpoint that the final written law will be in favor of whoever has the most lawyers.
It's actually simple. Take David Attenborough's name out of the picture.
"A generic British guy is now narrating my life" isn't as funny as implicating a known celebrity, which is where the legal issues would arise. A generic British guy isn't going to sue you.
Hell, you might even be able to get away with "A generic British guy who sounds like David Attenborough is now narrating my life."
Where to put the bar is a specific issue, but the exemplars in their category stand out as recognizable.
By the same logic, all simulated faces look like some real person somewhere, but I wouldn't expect to simulate a face that looks like Brad Pitt and then use it in a TV commercial