I much enjoyed the show.
It seems to me that the one big mistake that Sinclair made was to call the C5 a "car". In the run-up to the announcement (which I remember) the press were saying that the - then very successful, very cutting edge - company would soon release an electric car.
Of course it wasn't a car, it was an electrically assisted pedal trike. I wonder if it would have done better, if promoted as such.
The 15 mph limit still applies now to electric bikes, of course - but to be honest, I'd rather set out on a journey on my electric bike, than a C5 - better visibility, for me and of me, and easier to pedal/steer. It also reverts to a thoroughly usable pedal bike, with not much penalty other than weight, when the battery runs out!