As soon as these electric cars are on the road in meaningful numbers, the free changing/free parking/free congestion charge will stop. Cheaper motoring for greenies (ignoring the extra expense these cars are to buy) is great when the 2% are doing it and the 98% are subsidising it, when that number becomes 10%/20%/30%, that lost revenue has to be made up somewhere.
The immediate future of cheap motoring without huge additional costs in car tech would be an LPG powered GTI, but how long do you reckon LPG would stay at 70p a litre? I'm sure it would be easy enough for them to do a "hybrid" GTI that combusted petrol in the usual way when you want performance, but seamlessly burns LPG for up to 100PS requirements when you're just tootling on or cruising at a set speed, and it would cost very little extra to do. A little space lost in the boot for the LPG tank. I'm sure VW do something similar already (albeit not for the performance models), for other markets.