I see
ZapMap has a basic calculator to allow fuelling comparisons between vehicles - could be electric/electric or electric/fossil fuel. The cars in the database are not the most up to date - doesn't have the new Renault 5 for example, but does give a good idea of comparative costs.
Based solely on fuelling costs, my Yaris hybrid would cost just £30 less per year than an MG4, based on £0.50 per kWh and 100 miles a month. Or to put another way, insignificant.
If I change the charging price to the usual price around me of £0.79, then the price difference is still only £130 a year more in fuelling costs to go electric.