I know someone who works for the public sector. Their colleagues have electric cars, they charge them at work for nothing. For all I know they may drive home then run their entire house from the car battery.
At the moment there are some very good perks for some employees with these things. But I'd hope that this will end soon, as the novelty wears off and people realise they're not CO2-free or good for the environment.
The David Lloyd supposedly discounted prices are more than double any decent home tariff, they're taking the pee. But if you have a leccy car then you'd have a tariff that lets you charge for a lot less, or even for free if you have solar panels.
Having a terraced house probably means you're stretching to justify getting one. Just accept that they're really only for richer people with driveways. Unless your council would allow you to put a duct across the pavement for charging, but even then you need to think about how often you can actually park outside your own house - when I lived in a terraced house that was hardly ever, often I parked in a different street.
Don't forget that the government will charge you a further 3p per mile on top, equating to £300 a year for 10,000 miles, while charging petrol or diesel drivers nothing (although of course they pay fuel duty).
I'd suggest forgetting the whole idea. They don't really make financial sense, yet at least.