Ok, here's my calcs:
Currently petrol costs 1.41 (where I live) or 1.54 or so at motorway pumps.
Currently I drive 1.3 l turbo charged Nissan Qasqai. With the full tank of ~55 liters, I can do ~500 miles on motorway at motorway speeds (cruise at 74 mph). Or ~350 miles in towns. And this cost me more than 70 pounds to fill at the cheapest price I can get (all other pumps I see around me are higher than 1.41).
For 500 miles I would need probably ~ 2 full charges of 75 kWh. So, in total this would be 150 kwh (please correct figures if I am wrong here) for 500 miles
So in order to charge to 150 kwh for 70 pounds the price per kWh should be 46.6666 p per kwh