I'm sure we have done this before.
3.5 hours to charge from flat. asumming 10amps for the full period (known that the last 30mins is less )
3.5 * 10 * 220v = 7,700
12p per Kwh
.12 * 7.7 = £0.924
So take the time to charge multiply by the voltage and current (3.5hours * 200Volts * 10amps)
Divide by 1000 to make Kilowatts.
Multiply this my what you pay for your KW/H (12p)
So a free charge can be worth £1.
Solar charging savers you £1
What starts to get more interesting for me is the Petrol comparission.
1 gallon of petrol is around £6 so multiply your range by 6 to get (6 * £1 charges) to get yout equiverlent range.
6 *44miles = 264 mpg.