Vw polo 9n3 blue motion. We are about to sell ours, it's a later development of the 3L/100km motor in the a2. Can do exactly same economy as a 3l, my record to date is 85.5mpg brim to brim, and does an actual 70mpg whilst doing motorway work at normal speeds (70 to 85).
The a2 tdi with the vnt turbo are starting to go up in value, the 3L are all gone or in collections by now I think.
Honda insight (90s one) and BMW i3 are similar levels of madness to an a2.
Will prob get an a2 at some pont in the future. They are an unusual beast, a physically small car, that's light, drives OK (no handling car!), very economic, but also a nice place to be, seats and interior fit and finish is excellent. Very practical with a deep square boot and back seats come out completely I think.
Insurance is high on them I think because no one can repair them but tbh never tried as haven't owned one.