This completely depends on your car and the price per kWh that a charge point operator charges. If you’re charging at home, the price per kWh depends on your electricity provider. The calculation of this is to times the size of your battery (kWh) and the cost of electricity (pence per kWh).
Look into off-peak charging options. Charging after 10pm would be cheaper than charging at 6pm, when most people arrive home from work.
As a rule, rapid charge stations will be more expensive per KWh than other options.
Similar to petrol and diesel fuel, pricing for charge will also be more expensive at service stations on busy motorways.