But three quid you quote at a UK average of 34p per kwh hour (Source- Energy Saving Trust) will only get you 8kwh of power....you wont get far on that. So with an efficiency rating of what? say 3 miles per kWh that 3 pound will get you about 24 miles! I can get further than that on £3 worth of diesel on a motorway trip....and only a little less on my commute.
I don't have a home charger, I only charge the car using public chargers (Ubitricity lampposts).
At the height of the energy price crisis, I was being charged 45p per kWh (now gone down to 37p). My car averages 4 m/kWh (5-6 driving in the city, 2-3 on motorways on a cold day). That's around 11p per mile at the peak.
My ICE car (Suzuki 1.6L) does 300 miles on a full tank, which is 47L, about 10 Gallon. At 30mpg, that's around £60 worth of fuel, or 20p per mile.
If both cars are driven in winter at motorway speeds, then their cost-per-mile might come close to each other, because the EV's consumption will become worse while the ICE car's mpg will improve.
BUT: My calculation is based on the price of electricity at the charger in front of my house. On one hand, if you have a home charger, you'll pay significantly less than that (plus you'll benefit from the energy price cap), but on the other hand, if you use public ultra-fast chargers (350kW) you'll likely pay double what I paid.
My point is that there could be a particular set of circumstances where the energy cost for an EV per mile is the same or higher than that of a comparable ICE car, but it will be a unique and fairly rare set of circumstances. For example, if your neighbour regularly used his EV for long motorway journeys on cold days and charged it using fast chargers in motorway services. But in the vast majority of cases, the cost of the energy required to propel an EV will be significantly lower than that of an ICE car (in great part due to the difference in taxation/duty). For this reason, I would take your neighbour's story that "When the cost of electricity was at it peak price a few months back it was costing my neighbour more to run his EV 308 Pug than his wife's otherwise identical (even down to the same bright blue!) diesel version" with a pinch of salt.
EDIT: Just saw what clk320x is paying for his electricity...