Addison Lee would be my prefered choice.
Black cabs are licenced to rip you off... the driver has free choice over any metered route regardless of distance*.
This is utterly contrary to Hackney carriage licensing outside of metropolitan London where the driver must know,and use the shortest distance for any metered journey... any agreed fare must be less than or equal to the metered shortest routed. Applying the Uber model to TfL licenced taxis would make them more efficient and protect customers from over charging. In its current guise, as a hailing service using private hire drivers, uber circumvents alot of the licensing regulations.
Although several councils now seem to be addressing this issue by obliging Uber to establish local hubs using locally registered and licenced drivers... without applying it is difficult to see whether the Operators licences are held by Uber or if the drivers must have their own
If the former, then Uber are embracing their legal responsibility for their customers and drivers... if the latter, then it's all on the drivers, in which case the drivers have no protection from Uber and their terms and conditions or charges...
*Private Hire fares are different in this regard as they must simply be pre advised/agreed at the time of booking if no meter is used.