A managable speed
We are frequently told that the average speed of traffic in Central London (as an example - probably the worst example) is only 9 MPH [ source: TfL ]. Now obviously this conceals more than it reveals: there are still a few times of day when you can get 100 yds of clear road and really put your foot down (on the clutch, from 1st gear into second).
But it would seem that these driving conditions would be ideal for a Wonka-mobile. Apart from ferrying various forms of drunk around the city, it would be the ideal means of transporting packages and goods. The lack of a human driver should do wonders for pushing down the cost per hour of freight and you wouldn't have to give this thing a tip (unless you were trying to roll it over) or listen to endless chatter gleaned from that day's Daily Mirror. If it also removes the vastly oversized and frequently nearly empty red buses from London's overcrowded streets: where the cars parked on either side means that in suburban roads it is impossible for them to pass one another, then that would make a Wonka-mobile worth it, on it's own - and might even drive up average speeds to a mind-blowing 10 MPH.
Best of all, it might just put the shoe on the other foot and get Uber drivers complaining about the unfair competition.