The British list would appear to have some omissions. E.g. online real-estate site Rightmove (LON:RMV - has market cap $3.76Bn) is bigger than JustEat and Wonga.
Adam, thanks so much for the information. Indeed, our World Startup Report was not aware of this company. We will update our data (can't promise that the Economist will change their infographic though). Thanks again!