The UK Governments Energy Price cap that comes into effect on October 1 favours EV's .
With price of electricity capped at 34 pence per KW charging a mid range EV such as as Nissan Leaf from 0 % to 100% will costs around £20 to charge. A Nissan Leaf has a WLTP range of 239 miles which translates to 8.36 pence per mile.
If you take an ID3 or a Tesla Model 3 the cost for a 0% to100% charge is slightly more at £23.80 which translates to 9.95 pence per mile.
Comparisons with fossil fuel vehicles is difficult with Petrol and Diesel prices varying but a standard example of a similar car to the ID3 is a Golf TDI . The Golf achieves 50 MPG on average. If Diesel is assumed to be £1.85 per litre the cost per mile for Diesel in the Golf is 16.8 pence per mile
As can be seen charging an Ev under the energy price cap still remains cheaper than fossils and the price is guaranteed for two years