Another problem is how long does it take to charge the damn thing up. Substantially more than a petrol fill up. And aall of these disadvantages for £20,000 subsidised.
Why would you drive it to a filling station to plug it in for several hours when you've got perfectly good electric at home?
The Leaf has a range of ~80 miles, but only a nutter would plan to drive it 80 miles every day without a charge, so let's assume you drive a 50 mile round trip to work each day.
Petrol is currently nearing £6 a gallon, and a typical car does 40mpg - so, that's £7.50 of petrol a day... They reckon a Nissan Leaf uses 2.5p/mile of electricity (not sure what assumptions they make there though!), so that would be £1.25 for the 50 mile round trip. Even if you're comparing it to a super-efficient-ultra-frugal diesel that gets you 60-70mpg, you're still saving £4 a day on fuel.
For an effective after-tax payrise of £1500 a year, I would be more than happy to plug my car in each night after parking it on the drive. If you can afford to pay £20K for a car then you're almost certainly paying 40% tax, so in reality you are taking a £2,500 payrise.
Only problem with this argument... it assumes you don't expect to drive the car too far each day, or do it with any sort of performance. Plus, the connector is under the front cover, so you'd have to reverse off your drive.