You can hang a wire out your window etc. to your car, however you then have to ensure the cable is clearly marked and isn't a trip hazard as you'd be liable.
You're also going to have a pretty low kW per hour this way, so a charger on the wall would be best, but you're still having the same issue. 7p per kW is great though!
The ones in lamp post (Shell Ubitricity) are about 5kW per hour, and it'll cost you close to 50p per kW hour on a tariff - this isn't particularly quick nor cheap.
Some of the lamp post ones though are up to £1 per kW if it's a PAYG. Near to Lark Lane, you do have the ones in McDonalds, yet they are 87p per kW hour.