I'm not really convinced yet by the electric motorcycles except for two specialised purposes. One is road racing and the other is MX-Enduro-Trail. Both assume you've got a trailer and probably a generator and/or a spare set of batteries. Piaggio look like they're getting there with a hybrid, but you gain a lot of weight and lose a lot of luggage space in the process. Essentially silent trail bikes make trail riding almost as invisible as bicycling. And silent MX opens up urban and suburban MX tracks.
However it is possible that in London or other similar cities there may be ways of charging at both ends of the journey that make predictable journeys possible. At that point the free parking/road tax, no congestion, silent, low insurance and being pollution free (at street level) might become attractive in the same way that the G-Wizz is attractive.
BTW. The latest G-Wizz uses LiPo batteries for a 50% increase in price. It makes for a much more interesting machine, but £10k ???