Thanks Phill. I've seen quite a few cyclists riding around Central London with 2 very large hub motors in each wheel on a full suspension frame. Incredible warp-speed-like performance. Didn't spot a number plate, nor any form of registration. I guess it's up to the policeman's discretion if your ebike is still a bicycle or a moto-ped.
RE: The action camera. I bought my HD Drift Ghost S as it has the car DVR facility. It records continuously, and saves the data in the event of a knock, etc. The latest firmware has improved the video quality, but the GoPro has the best image quality.
But yes, boy do i regret not having wiped the card and recorded the accident. MicroSD cards are cheap. My 64 Gb Class 10 Transcend Premium MicroSD card was £32 off Amazon. I wish I'd bought 2 of them and swapped them round every other day.