At £6 per gallon and 50mpg - equivalent cost of petrol
£82 lease fee = 14 gallons of petrol which is 700 miles per month or 8400 miles per year.
£2150 to buy= 360 gallons = 18,000 miles total
Added to this is cost of electricity still required to charge the battery, about 6 pence per mile at normal rates per KWh.
A petrol car doing 50mpg is about 11.5 pence per mile, so 'saving' of 5 to 6 pence per mile.... with diesel the 'savings' are even lee impressive, maybe 3 pence per mile. This ignores the existence of a dedicated home charger ( £2000 installation cost less £400 grant ) or a 'power wall' ( £10,000 + solar panel cost ).