The lightweight "Lupo 3L" 1.2 tdi wighs 805kg, the 4 door Audi A2 version 820KG
in 2013 VW launched the XL1 hybrid, which does 310mpg, and in all electric mode has a range of 22 miles, and is lighter than the Lupo 3L at 795KG due to extensive use of composites. Perhaps range could be doubled with a modern battery today. It manages 6.2 miles per kwh. Tesla haven't broken the 5 miles per KWH yet with a production vehicle, and this is a 10 year old hybrid.
VW have continually commented that people don't want eco and fuel economy enough to pay for it.
A hybrid conversion on a Jensen might be much more beneficial than all electric with 50 mile range. Using electric for stop start and in town makes a lot of sense, a 10 mile range would be sufficient for many, a smattering of V8 growl from the lights, regenerative breaking, then silence and economy. Alloy parts for the engine would offset battery weight, at least in part.