Although I'm sceptical about the take-up speed in the UK, it has to be pointed out that Google's driverless cars have logged more than 1.2 million miles on the roads (not test tracks) of the United States:
https://en.wikipedia.org/wiki/Google_self-driving_car#Road_testing
In June 2015, the team announced that their vehicles have now driven over 1,000,000 mi (1,600,000 km) ... and that in the process they had encountered 200,000 stop signs, 600,000 traffic lights, and 180 million other vehicles. Google also announced its prototype vehicles were being road tested in Mountain View, California. During testing, the prototypes' speed cannot exceed 25 mph (40 km/h) and will have safety drivers aboard the entire time. As a consequence, one of the vehicles was stopped by police for impeding traffic flow. As of September 2015, Google had test driven their fleet of vehicles 1,210,676 mi (1,948,394 km). Google has expanded its road-testing to the state of Texas, where regulations do not prohibit cars without pedals and a steering wheel.