Exactly oscarmax and on top of that there are only a handful of cars capable of bi directional charging in the first place. Interesting VW, from next year, will be one of them and VW have been motability partners for years. So hopefully next year will bring some more choice to the scheme.
As well as the Nissan Leaf the Mitsubishi Outlander PHEV is capable, it has a 13.8 kWh battery with 10 kWh usable capacity just sitting there and waiting, instead of exporting from our PV panels to the grid for 4.1p kWh, I could store that energy in the PHEV and save myself few quid, the equivalent same size Tesla battery bank £8,000 + Vat
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.