My fuel costs are about 15p/mile in my old rustbucket (45mpg is about 10 miles per litre, £1.50 a litre)
An EV will do say 4 miles per kWh, so in theory at 30p/kWh that's 7.5p per mile, half the price.
5000 miles a year that's £375 saving with electric. Add in another £160 VED saving (again my old bucket) and that's £500 a year.
A bottom of the line Micra is about £13k new. A bottom of the line Leaf is £27k new. A new micra will get better milage and lower VED than my 20 year old one too.