OK I think I have decided against a Leaf. The main issue is that it won't work for me as an only car, so i need to keep the Mazda estate. However, that means I keep the expenses and inconvenience of an old car, and make no overall savings. Indeed, the £70/month battery charge would offset most financial benefits - that's about what I spend on fuel apart from long journeys.
But the basic principle of having an electric car is, I think, OK for me, despite the fact that we have no drive. So when there is a larger one at a sensible office, I think I'll make the jump.
Good luck with yours Jack